No idea what's wrong here, and I'm useless when it comes to hardware issues.
I just want to make sure I'm chekcing the right things and changing the right parts.
PC bought in Dec. 2008 (Quite recent)
DP45SG Intel Mobo
ATI 4870 Radeon
Core 2 Duo E8400 3GHZ
2X2Gig Kingston DDR3 RAM
Corsair HX 620W PSU
Running on Vista.
I've been getting a slew of issues with my PC that have gotten me pulling my hair out. It started off with random crashes that wouldn't let me boot my PC after for several hours at a time. It happened one or twice a week, but after they happened, I couldn't use it for nearly 2 hours. The LED's would start up, the fans would all start, but I'd get no POST, no signal to my screen, no sign of life. Basically, my computer just got power running it, that's it.
So I brought it in the the shop I bought it from and that assembled it, and they told me that the Video card had been lodged out of place and that it was creating an electrical short in the PCI slot which was making the PC crash and not boot up. They said they fixed it, and eventually told me that should it happen again, just to push the my Video card in a bot cause due to using Dual display, the weight of my ports on the back of my card was making it bend a pbit and in the long run, it was making it shift, causing the short.
So I brought it back, and it crashed again after a week, and I puched my card back in, and it worked fine, for 3 days... I went on and on like that, every time the computer working for less long every time, to a point where I booted it and within 5 minutes it would crash.
Since I intended to upgrade my video card during the holidays anyway, I went and got me 2 Radon 4890s. (My computer has been idle for about a week now) And that's where I'm at. I put one 4890 in and plugged it, and my computer wouldn't even boot. No power at all. No fans, no LED's, no sign of life. The power light on my Mobo is still on though, strangely enough. Now given what I've read I thought it was the power supply that's borked, but if that was the case, I wouldn't get the mobo light turning on.
I've taken my video card off the jumper already and checked it, even put my old one back in and it's still not working.
Ok first thing I would check is the power supply - as some of the issues you describe could be a weak PSU.
If you dont have a spare PSU unplug every non essential device in your PC (DVD / CD drives etc) so you should have just 1 x HDD, mobo, 1 x stick of ram and your video card. Try re-booting and see if the PC remains stable enough that it doesnt shut down randomly.
PCIE graphics cards have a latch / tab mechanism that is supposed to stop the card coming loose, and also should have a screw securing the back plate to the back of your PC case. I dont believe the card coming loose is a genuine reason...
The power light on my Mobo is still on though, strangely enough. Now given what I've read I thought it was the power supply that's borked, but if that was the case, I wouldn't get the mobo light turning on.
Common misconception. That LED is is illuminated by the Standby Power Supply. That is a small, always on, 5 volt power supply that is completely separate from the circuits that provide operating power to the computer. All it basically indicates is that the PSU is plugged into the wall and turned on.
Your Corsair is a better than average PSU, but anything can fail.