Stability trouble, random restarts and freezes

[FireGryphon]

My desktop is about three years old now. in the last few weeks its stability fell through the floor. On average, once a day it'll either freeze up or randomly restart. Sometimes on boot, Windows will not load fully, and I'll have to restart again. Tonight it randomly restarted twice so far, so I figure I should get to the bottom of whatever it is.

Besides the seemingly random restarts and freezes there is one other symptom. A couple weeks ago the computer would not POST and gave a beeping noise that I gathered, via calling a friend and having him look up the mobo manual, meant that there was an error with the graphics card. A few restarts did no good, and the card seemed to be securely in. I didn't have a screwdriver handy to reseat the card, so I laid my tower case on its side. That miraculously solved the problem, and the case has been on its side ever since.

There are a few things I figure it could be: PSU, RAM, or the graphics card. Even though the only specific error was the graphics card I somehow doubt the graphics card could cause random restarts. I don't have any spare hardware to swap, so I'm in a bit of a tough spot as far as troubleshooting this thing goes. Best I can do is Memtest86 overnight and see how that fares.

Is there any troubleshooting method I'm overlooking?

[Chrispy_]

Sounds like something (probably the graphics card) was bending under its own weight and a dry solder joint has cracked somewhere over time.

With the case upright again, check that the machine fails to POST again and then with something plastic support the card's weight by pushing up on it gently.
If it POSTs again, problem identified.

Other things to cause problems based on the orientation of the case are:

a loose screw shorting something
a loose cable
flex in the case causing the motherboard/PSU/expansion cards to bend and lose contact along things like DIMM and PCI-e connectors. (if it's a cheap, flimsy case)