Computer sort of "shuts off" on me

[Tierra3690]

If anyone can help me I'd be super greatful!

Heres my problem: I will load my computer up, it will work just fine for like 3 minutes, then my fans will stop (I opened it up to see this because it stopped making noises) My monitor will say no imput or power signal, yet my tower liights are still on. I have a little green and red power light. Both are on.. So my computer is still getting power... but whats wrong? And how should I fix it?
Another thing. If it does this the only way for me to "fully" shut it off is to hold in my power button, or pull the plug. Then if I try to restart it it will shut off on me quicker than usual (possibly overheating? idk.) Sometimes while loading up it will say Drive A error and then in just a second shut off like it has been.

Does anyone know whats going on with it?

[ale52]

Sounds like a defective power supply.  Disconnect all your other devices (cdrom, floppy) remove all expansion cards (network, sound, etc.) and reboot.  Does the problem still exist?  By removing these items it rules them out as a culprit. 

Alan <>< 

[Tierra3690]

I dont have a floppy disc drive ( which is why I was wondering about the drive A error?) and I dont think I have sound card expansions or anything (atleast nothing that I put in it since buying it) but I do have a cdrom drive.. so to disconnect... do you mean open it and take it out? because I cant disable it if it involves my computer being on.. as it doesnt stay on for very long..

[street1 (RIP)]

Have you made any changes in the CMOS/BIOS settings?

[Tierra3690]

nope, i havent made any changes. It just happened one day and has been since.. It started doing this about a week ago.. I was in the middle of doing an essay and it just shut off...

[street1 (RIP)]

So,I am thinking you need to clean your computer. Apparently!

See below site.

http://www.technibble.com/how-to-clean-the-inside-of-a-computer-case/