Startup BSOD

[Pavilixn182]

I received the PC as a gift because a friend didn't want it. It was dirty and I give a good hand of maintenance. Okay. Everything was perfect as it started working correctly (previous issue wss that it didn't want to show anything in display, I fix that), until Windows 10 started booting saying it is givinga diagnostic to the PC, and then it comes the BSOD with the DPC_WATCHDOG code, which means something is wrong with a hardware element. But I haven't install anything on the motherboard (yet). And I tried and I tried with other several hard drives, specially with one, 80GB Win7 64x. I thought the problem was gone thinking it was the PC'S OG HDD, but I got BSOD again calling for the code 0x0000007b. I immediately changed my mind. Took out the RAM, added a new one and it continued showing the BSOD. Disconected some cords and resetted CMOS and same results. Tried to reinstall Win7 via USB but process stood stuck in the "Windows is preparing services" screen, which I wasn't allowed to get to select the HDD I wanted to install the OS. Haven't tried with a booted DVD CD yet. Help me, please. I have nothing else to do! 

[WAWood]

@Pavilixn182 

Bluescreen failures (i.e., BSODs) are notoriously difficult to diagnose and to fix -- far beyond what WE typically can do in THIS self-help Community.

What you need is a forum where folks have vast experience troubleshooting, diagnosing, and suggesting repairs for BSODs, as follows:

The community Win7 forums has a section devoted to diagnosing BSODs. So, your best bet would be to post your problem there: https://www.sevenforums.com/bsod-help-support/

Good Luck