Windows XP, most recent SP and all drivers up to date.
No recent installations of any software (including malware/virus, I've seen what that's done to my less wary family members so I'm very on top of things in that regard)
No new hardware installed.
No error messages during POST.
If you need any more information, I'll do my best, but I can't really get anything within the computer itself, of course.
Thanks in advance for your input, everyone.
Edit: Also, if everyone agrees that its the power supply, or I decide on my own to replace that, I may ask for some suggestions for a new one, if anyone here can provide help with that.
Edit2: Just powered it up again, had the tower laying on its side and I emptied my last can of air getting as much dust as I can out of there, especially around the power supply itself...It actually let me log in this time, everything loaded, and I thought perhaps clearing the dust fixed it...the fan was making a weird noise, and then it sped up quite a bit, and got a lot louder before shutting down...also, I have a fan speed/temp thing on the front of my case, it says the fan is going 9990rpm, which its not...it normally runs at 5400rpm. My CPU is also water cooled, and the tubes are looking very cloudy...there's like...a large cloud right in the middle of one of the tubes. Might that be preventing my CPU from being cooled, and so automatically shuts the PC off? I may wait to buy a new power supply until I clean the tubes...that may be my problem.
Edited by Syst3mcr4sh3r, 30 January 2009 - 10:24 PM.