PC crashing.

Somewhat vague title, i'm sorry.

So I needed a PC to host a custom Minecraft server, since my own PC isn't powerful enough to both host it and
play it at the same time. My dad had built a PC for my mom some time ago, and she wasn't using it anymore so
I decided to use it. It had more malware and problems than was worth dealing with, and was running XP because the software she was using wouldn't run on 7. I cleared everything off of it and installed Win7.

At first glance, everything seems to be running fine. I can lauch my game just fine and it works for a little while.
But after anywhere between 10 minutes and an hour or so, it freezes. The screen turns to multicolored vertical lines with varied widths, and the PC is unresponsive to anything short of Holding the power button down until it shuts off, and rebooting. This is where I'm at now, but its slightly(?) more complicated.

My dad figured it would need more ram than it had to run Win7. It had 4gb (2x2gb) As far as I can see, it seems to run ok with 4gb aside from the crashing...

He ordered two more sticks of ram (2gb ea) that was supposed to be the exact same thing that was already in the PC.

When they got here, we put them in and the pc booted to the desktop, but then crashed. My dad says they are the same thing, but the ram chips are slightly different in size etc. I tried switching their positions, I tried running the PC with only the new sticks, and with only the old sticks. It crashes before the desktop, or shortly after anytime the new RAM sticks are involved. Right now I've got the old sticks in there in slots 2 and 4.

Also, at some point someone thought removing the cmos battery for a few minutes was a good idea. No clue if that messed anything up.

I'm certainly no ace at PC hardware, so there is a high chance I've screwed something up somewhere.

Old Ram: Kingston KVR1333D3N9/2G 2GB PC3-10600 CL9 240-Pin DIMM

New Ram: Kingston 2GB PC3-10600 DDR3-1333MHz non-ECC Unbuffered CL9 240-Pin DIMM Dual Rank Memory Module Mfr P/N KVR1333D3N9/2G

The old ram plastic case has a kingston label on it, and the chips say Kingston, with various numbers on them. The new ram came in plastic cases that had no label. The ram sticks are nearly twice as wide as the old ones are, and the chips say ELPIDA on them. The above information for the old ram is taken from the label, the information from the new ram is from the order slip that came with them.

So I suppose I have two problems?

I'll gladly provide any addition information you need as best I can, and very much appreciate any help you can offer. :)

Sounds like a graphic card problem.Open up the case and remove the card,clean out the case using a vacuum cleaner or compressed air.The card is either actively cooled,using a fan,or passively cooled,using many fins.If active,then clean out the fan's intake and exhaust louvres and check the fan freely spins.If the card is old,4 years plus,the thermal paste may need to be replaced and the card's contact pins,gold coloured, should be cleaned,using a clean pencil eraser.

Thanks very much for the reply, I took out the graphics card and cleaned it a bit, and I ran the pc for five hours yesterday and 12 hours so far today. No crash yet . I'm gonna leave it running overnight and if it doesn't act up I suppose I can start
hoping and assuming its alright now. I'm not gonna mark this as solved quite yet, mostly because it hasn't been that long and It could still die on me. But also because there is still the issue of the new RAM not working.

Fingers crossed there aren't anymore crashes.It is preferable to keep RAM sticks matching and my Win7 works fine on 4gb.

Ok so it crashed again. I left it running when I left home a few hours ago and came home to an unresponsive PC. Should I look at buying a new gpu?

Edit: Just realized this is probably relevant. After cleaning the gpu, I did not put the side panel back on the case, I left it off for a while, including the five and twelve hour tests. Before I went to bed, I put it back on last night, and if its overheating I'm guessing thats significant?

There are a few more things you can do before buying a new card.Check the card for signs of discolouration,which would indicate overheating and inspect each capacitor {cylindrical components} for ANY distortion,if present then byebye card,unless you're game enough to solder on new capacitors.The thermal paste,between the fan/fins and card can be replaced by first removing the fan/fins,secured by screws,then gently scraping away the old paste using an old credit card or similar,NO METAL,then swabbing with Methylated Spirits and a lint-free cloth,Just use enough paste to finely cover the surface,it is there to help transfer heat,not block it.Finally,if you can borrow another known good card then try it to prove whether your card is working or not.
With regards to Gator's comment,yes the vacuum cleaner can be a problem.However I've used it for many years and always leave the case earthed by the cord,plugged in BUT swiched off and not touch anything with the nozzle.A bicycle pump is a good source of air,for blowing purposes.

At this point its not crashing any unless I put the case cover back on. The card looks fine, I don't see anything that looks out of place or anything. I'm gonna call it overheating and be done with it. Probably needs thermal paste. Thanks alot for all the help guys. :)

One last try,replace the case exhaust fan with a new one,they're only a few dollars.Overtime their efficiency falls away and just check the case vents for dust,etc.Over heating is a constant problem,the frustrating part is tracking down the cause.