Won't boot after component swap

I had this PC case just sitting around collecting dust for about 18 months without a CPU or any RAM. I finally scraped enough cash together recently to pick up some parts. The processor is used but was tested and confirmed working, and the RAM is brand new from the store. After I got everything assembled properly and hit the power button, the fans spin up, the motherboard LEDs light up, and I can hear the hard drive spinning, but there’s absolutely nothing on the screen—not even a single beep from the BIOS.
The monitor itself is fine; I’ve checked it, and it won't display anything whether I use the integrated graphics or the dedicated card.
I gave the whole thing a thorough cleaning with a compressor, so I'm ruling out dust buildup as the culprit.

Specs:
Motherboard - MSI 880GMA-E55
Processor - Intel Core i7-950 Black Edition RAM
RAM - G.SKILL Ares 2x4GB DDR3 1600MHz
GPU - Radeon VTX3d vx4850
HDD - Western Digital 500GB 16MB cache
PSU - Generic 550W (the label fell off, so I can't verify the brand)

Maybe try borrowing some "G.SKILL Ares 2x4GB DDR3 1600MHz" RAM from a friend or a neighbor and see if you can get the PC to boot using 1333 MHz instead.

What’s interesting is that the motherboard doesn't explicitly list support for that specific processor model click, which honestly makes zero sense since it supports nearly identical chips (it really ought to work). Bottom line: as long as you aren't running into any RAM compatibility issues, I’d definitely recommend flashing to the latest BIOS just to be safe.

That’ll probably end up becoming a meme, honestly. I’d actually prefer grabbing some used sticks over brand-new ones straight out of the box—you just never know if you're getting a dud right off the shelf. Though, there's a fair chance it's just a compatibility issue. Maybe try testing it with some different older modules first, and then you could eventually look into flashing the BIOS.

Yeah, you might want to try flashing the BIOS. If you can actually get the computer to boot up first, of course 😁

Thanks for the suggestions. If I run into anyone running Intel Core i7-950 Black Edition RAM, I'll let you know if it actually worked.

Try clearing the CMOS. I had the same headache when I swapped out my old Athlon for an Intel Core i7-950 Black Edition RAM.