Upgrading RAM on HP Compaq dc7800 Intel CoreDuo E7400 2.8GHz

[CWX]

I am running Windows 10 (64 bit)

When I got it refurbished from Best Buy it came with 2gb Ram sticks, one in slot 1 Bank A and one in slot 3 bank B.

I got four new 2gb sticks off amazon. I tried with all four 2gb sticks and then again with just one, both times it beeped and didn’t boot.

I tried again with only two of the new sticks the way it was before and it boots, so I think the sticks are good.

What am I missing? Is there something special I have to do in the OS to get it run with something other than 4gb installed?

[NonSequitur777]

@CWX,

Welcome to our HP Community forum!

I have researched your question using AI tools available to me -filtered, edited and adjusted based on my own experience.

RAM Known to Work with HP Compaq dc7800:

The dc7800 is based on the Intel Q35 chipset and supports up to 8GB of DDR2 across 4 slots. To guarantee compatibility, the modules should be:

• DDR2-800 (PC2-6400) or DDR2-667 (PC2-5300)

• Unbuffered, non-ECC

• 1.8V

• Low-density chips (avoid high-density "16-chip" or "8-chip single-sided" server-style modules)

---

Tested and Recommended RAM Brands/Models:

These models have been confirmed by users and refurbishers to work well in the dc7800:

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🔹 Crucial CT2KIT25664AA800

• 2x2GB DDR2-800 (PC2-6400)

• CL6, 1.8V

• ✅ Dual-channel, non-ECC, unbuffered

 

🔹 Kingston KVR800D2N6/2G

• 2GB DDR2-800

• CL6, 1.8V

• ✅ Very compatible with older HP/Compaq desktops

• 🔎 Look for “KVR” (Kingston ValueRAM) line -not server ECC versions

---

🔹 Samsung M378T5663QZ3-CF7 or Samsung M378T5663EH3-CF7

• OEM-style DDR2-800

• ✅ Used in many HP OEM systems

• Often found as used/refurbished modules on eBay or Amazon

🔹 Generic (inexpensive) RAM Options

• Example 1: https://www.amazon.com/Royemai-DDR2-800U-PC2-6400-Unbuffered-Computer/dp/B07WMP4TQG/ref=sxin_16_pa_s....

• Example 2: https://www.amazon.com/Udimm-Unbuffered-Desktop-Memory-Modules/dp/B08V85C5KJ/ref=pd_day0_d_sccl_2_1/....

• ✅ Dual-channel, non-ECC, 2Rx8, 6400U, 1.8V

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Avoid These Pitfalls:

• ECC modules: Often labeled “PC2-6400E” or “PC2-5300F” – not compatible.

• High-density modules: Often used in Dell or servers, not desktop-friendly.

• 2.0V or higher voltage RAM: Can cause boot failures or instability.

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Final Tips for Installation:

• Install in matching pairs: slots 1 & 3, then 2 & 4.

• Boot after installing just 2 sticks -then add the other 2.

• Update to BIOS v1.35 if not already installed.

Kind Regards,

NonSequitur777

[CWX]

Thanks for the quick reply!

I was able to get all four 2GB sticks working! 

My issue was that I didn’t have a VGA display and was using a VGA to HDMI dongle, and the boot menu wasn’t displaying over that connection.

I do have some follow up questions if you could help.

1) BIOS Update

I checked my BIOS as you suggested. I am actually on version 1.32, I am having trouble updating to 1.35. Windows 10 wasn’t listed on HP’s page for this machine, but after some more searching someone said to use the version 1.35 listed under Windows 7. I copied the contents from the DOS Flash folder to a clean FAT32 formatted USB and restarted the machine. Then I got the following message:

”Attempting to boot from USB device

An operating system wasn’t found try disconnecting any drives that don’t contain an operating system.

press any key to restart”

Any ideas?

2) CPU and GPU 

Now that I have more RAM, I think I’d also like to add in a GPU card and possibly upgrade the CPU.

I saw other threads on this, but they were a bit dated and I wish for advice current in 2025.

A couple of GPU’s I saw others had upgraded to we’re the MSI GT 1030 and the ATI Radeon 5450.

My question is in 2025 are these still good options?

Would the current Intel CoreDuo E7400 2.8GHz be enough to support those GPU cards? I saw someone say they upgraded to a Core2Quad Q6600.

Again my goal is to get the best CPU and GPU that I can in 2025 to future proof this thing as much as I can.

thanks so much

[NonSequitur777]

@CWX,

Thank you for the update -an outstanding job getting all four 2GB sticks working!

Yes, I would be happy to assist you further: in order to best assist you, I need to know whether you got an HP Compaq dc7800 SFF (Small Form Factor) or the HP Compaq dc7800 CMT (Convertible Minitower).

In any regards, let’s tackle your questions one at a time:

---

1.) BIOS Update Issue:

You're on BIOS version 1.32, and trying to update to 1.35 using the DOS Flash folder on a USB drive -but you're getting the "An operating system wasn't found…” message.

Here are some things to check:

• Ensure the USB is formatted as FAT32, not NTFS or exFAT.

• The USB must be set as bootable. Copying files alone isn’t enough. You’ll need to use a utility like Rufus to create a DOS-bootable USB stick, then manually add the BIOS files to it.

• Alternatively, if the system has a BIOS-level update utility (accessed via F10 at boot or a dedicated BIOS Flash menu), try using that with the USB plugged in.

• Make sure the USB is inserted into a USB 2.0 port, not USB 3.0 (older machines often have boot issues with 3.0 ports).

Let me know your exact HP model if you need a step-by-step walkthrough.

---

2.) CPU and GPU Upgrades (2025 Perspective):

Best CPU Upgrade: Core2 Quad Q9650:

• 4 cores / 4 threads @ 3.00 GHz

• 95-watt TDP -double-check your cooling solution and PSU

• Still surprisingly usable in 2025

• Compatible with most LGA 775 boards that already support Q6600

The Q6600 is a good upgrade from your E7400, but the Q9650 is the top performer. You can purchase one of these online, for as little as $33 via this trusted PRC Seller: https://www.ebay.com/itm/141823667427?_skw=Core2+Quad+Q9650&epid=96782124&itmmeta=01JV0R8D1HBCPWZYHC..., or around $100 via a trusted US eBay Seller: https://www.ebay.com/itm/353499441780?_skw=Core2+Quad+Q9650&epid=15029958281&itmmeta=01JV0R42BE6MA7D....

---

Best GPU Options (Low-Profile / Legacy):

Your motherboard’s limitations (likely PCIe 1.0 or 2.0) and power supply will constrain your choices. Here are current 2025-relevant options with your stock power supply:

• GT 1030 GDDR5 version (not DDR4!)

  • Very efficient (~30W)

  • Great for 1080p video playback, light gaming, and driver support still exists

  • Avoid the DDR4 version -it's severely underpowered

• Radeon HD 7750 (low profile if needed)

  • No external power required

  • Slightly better than GT 1030 GDDR5 in raw performance but older driver support

• RX 550 (with caution)

  • Low power, slightly better than GT 1030

  • Check case clearance and power supply capacity

---

What to Avoid:

• Radeon HD 5450 – Far too underpowered by modern standards; no longer worth installing

• DDR4 variants of the GT 1030 – Misleading branding and poor performance

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Bonus Tip:

After upgrading the CPU and GPU, consider installing an SSD (if you haven’t already). Even a cheap 120–240GB SATA SSD can massively boost performance compared to a spinning HDD.

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Let me know your exact desktop model number if you're unsure about compatibility.

Kind Regards,

NonSequitur777

[CWX]

Wow! Thanks again for such a complete answer, you are awesome. 

For clarity this is a dc7800 Small Form Factor.
System SKU : GC760AV
Processor: Intel CoreDuo E7400 2.8GHz
BIOS Version/Date : HP 786F1 v1.32, 7/21/2011
SMBIOS Version : 2.5

BIOS Mode : Legacy
BaseBoard Product: 0AA8h
BaseBoard Version: Not Available
Secure Boot State: Unsupported
PCR7 Config: Binding Not Possible
Boot Device: \Device\HarddiscVolume1

I am not sure if this tells you enough or how to tell the board revision, I think its "A" or "NXP MOS"

BIOS) {
I tried using the F10 boot menu and thats where I got the previous error message. I will try using a utility ensure the stick is set as "bootable" and report back.
}

CPU and GPU){
PSU) Model: DSP-240MB A REV 02F, OUTPUT: 240W MAX

CPU)  So I think I should have enough juice and the current onboard cooling should be enough, just need to swap in the Core2 Quad Q9650 with some new paste. 

GPU) Is there a way to tell if the PCI ports are 1.0 or 2.0? 
}

Further Upgrades) {
1) HDD to SDD - I think I would like to do this, but I am unsure how to transfer the OS and my precious files to the new drive. 
2) I do already have an upgrade card for USB 3.0
3) The only other thing I can think to get this machine the best it can be would be to add WiFi capability. Any recommendations would be welcome.
}

Thanks again and in advance

[NonSequitur777]

@CWX,

With your 240-watt power supply, I would recommend one of the following graphics cards -from lower to higher-performing cards:

1.) low-profile GTX 750 Ti

2.) low-profile RX 6300

3.) low-profile GTX 1630

4.) low-profile RX 6400

5.) low-profile GTX 1050

6) low-profile GTX 1050 Ti

7.) low-profile Dell Radeon RX 6500

8.) low-profile GTX 1650

9.) low-profile RTX A2000

Whatever low-profile card you get, make sure it has a low-profile bracket or else you will not be able to install it in your SFF case.

Cloning your SATA HDD boot drive to a much faster SATA SSD drive is easy, and there are many YouTube instructional videos available how to do that, and specifically using Macrium Reflect Free, such as this video: https://www.youtube.com/watch?v=Sh5QlDa8e64&ab_channel=OnlineComputerTips.

For Wi-Fi connection, one of the easiest ways to accomplish this is to use a USB dongle, such as this Amazon purchase option: https://www.amazon.com/Wireless-Adapter-Dual-Band-Antennas-Windows11/dp/B0DYH7RGDK/ref=sr_1_4?crid=Q....

Kind Regards,

NonSequitur777