hp omen 40L not turning on with new cpu.

[JOHN_MARSTON]

Ok, so i recently got an i5-14600k, upgrading from a 15-12400f. i updated bios then installed the cpu. when i turned on the computer, the fans spun a little and the system powered off. Any help would be greatly appreciated 

[BeemerBiker]

I had to guess at your exact model, but if you have the GT21-0000i type such as this one

then that CPU is not on HP's blessed list as shown here

Intel Core i5-12400 (2.5 GHz base frequency, up to 4.4 GHz with Intel Turbo Boost Technology, 18 MB L3 cache, 6 cores, 12 threads)	65 W
Intel Core i5-12400F (2.5 GHz base frequency, up to 4.4 GHz with Intel Turbo Boost Technology, 18 MB L3 cache, 6 cores, 12 threads)	65 W
Intel Core i7-12700 (2.1 GHz base frequency, up to 4.9 GHz with Intel Turbo Boost Technology, 25 MB L3 cache, 12 cores, 20 threads)	65 W
Intel Core i7-12700F (2.1 GHz base frequency, up to 4.9 GHz with Intel Turbo Boost Technology, 25 MB L3 cache, 12 cores, 20 threads)	65 W
Intel Core i9-12900 (2.4 GHz base frequency, up to 5.1 GHz with Intel Turbo Boost Technology, 30 MB L3 cache, 16 cores, 24 threads)	65 W
Intel Core i9-12900F (2.4 GHz base frequency, up to 5.1 GHz with Intel Turbo Boost Technology, 30 MB L3 cache, 16 cores, 24 threads)	65 W

Possibly the problem is the motherboard cannot supply over 65 watts to the processor.

That i5 requires up to 181 watts,

[NonSequitur777]

@BeemerBiker,

Because I dealt with a similar case before, I wonder if the OP got an OMEN by HP 40L Gaming Desktop GT21-2xxx as fitted with the ArcticU motherboard (SSID: 8A97) OR the ArcticOC motherboard (SSID: 8A96) which have the Intel Z790H / Z790 chipsets, compatible with 13th and 14th gen Intel Core processors, but because this PC was initially released for 13th gen processors only, the OP wants to make sure to update the BIOS to the latest version, which happens to be F.29 Rev.A for the ActicU motherboard, and F.33 Rev.A for the ArcticOC motherboard, both released on September 16th, 2025: https://support.hp.com/us-en/drivers/omen-by-hp-40l-gaming-desktop-pc-gt21-2000i/model/2101754548?sk....

Regardless of what Omen 40L model the OP got, making sure that the latest BIOS version is installed may fix this issue. Incidentally, BOTH ArcticU and ArcticOC motherboard versions allow processors with "TDP: Up to 125 W", so the OP's i5-14600K processor should not be problem.

Kind Regards,

NonSequitur777