graphic card failure/power failure

[boyboy400]

Hello everyone,
I bought this PC "iBuyPower Desktop Gaming Computer featuring AMD FX-4100 Processor (BC500)" 7 months ago. I also have a 21 Philips monitor.
Two days ago, I was working with it and the the screen went black (like the monitor goes sleeping) so I had to turn off the PC by holding the power key so it shut down. In a few seconds I pressed the power key again to turn it on; I heard the sound of fan a LITTLE BIT but the PC wouldn't turn on. The PC was under my table. So I put it on the table, open it up, clean all the dust, leave it on the table, leave the left door off (to keep it cooler) and it was fine.

Yesterday it happened again (the monitor went black) and I had to the same thing I described above but then I wasn't able to boot because some files were corrupted so had to use the Windows DVD to repair the start up.

Tonight it happened again plus something else. Imagine your monitor supports 1920*1080 resolution but you use a much lower resolution; how is the picture? Like low resolution like old computers. I was working and the monitor went like this and I had to shut it down. I restarted right away, booted up until I saw my desktop but then it shut down automatically in a few seconds (like a temperature problem?). I tried to turn it on again but heard the sound of fan for 1 seconds and it wouldn't turn on.
So I turned it off from the key at the back of the case, opened the left door of the case again, took the graphic card out and replaced it, opened my room's window (so it's freezing here) and now it works fine.

I don't know what's going on people. It's a gaming computer, the case is already like sieves!!!!! and here the weather is freezing like -13 although my room's temperature is not that cold but I mean it's not that hot over here.

The problem to me sounded like a graphic card failure. I felt opening the room's window and taking off the left door of the case, helped. Also when doesn't turn on, if I turn it off from the key at the back of case, it helps and the PC might turn on. Also hearing the 1sec sound of fan and then not turning on, seems like power failure! but I don't know

Could you please tell me what the problem is in your opinion?
I'm afraid if I sent it back to use the warranty, the problem doesn't show up for them and I just have to pay for the shipment
Thank you

what I'm doing now is to move some files from drive c (it has like 150G free but anyways) and then try to reinstall the windows. It doesn't sound like an OS failure though does it?

Sounds silly but the only software I recently installed (at least what I can think about now) is Eraser that causes them to be unrecoverable. May that be the problem?