Yeah, Think i will just change case's and get her a new graphics card then reinstall Windows with new Windows 7 THEN, Wait to see if it happens again......
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Well .. I'll give you $25 for the 9800, sight-unseen/as-is ...
First, with some deference to my compadres, there is nothing in your spec that is not up to the task of her needs AND (more importantly) ... betcha your lunch money ... there ain't nothing wrong with any of your hw components that a good, thourough, shake-down would not cure (COM-pletely).
Consider this (because I KNOW) ...
1) Any (purely) non-mechanical component that survives the first 90 days will last at least 5 years and maybe for 20, if it has proper power and cooling. (except CRTs).
2) Connections can (and do) vibrate loose (just sitting there) and, every time your GF moves the case (even just to dust), things get slightly more loose.
3) Oxidation (mild/microscopic "rusting") will degrade your original (good) connections, over time.
[ Reseating/re-connecting usually rubs the connection clean ... we have also used #2 pencil erasers, on card-pins, to clean them up (but DON'T)]
4) OS and App/Game updates can effect various driver versions/functions, sometimes requiring a co-dependent driver update.
5) Viruses ... Drive/file corruption ... accidental deletions, etc. ... can effect.
6) YOU SAID ... "Bumping the Case Causes... " ... A clear indicator of a sporadic/intermittent connection (problem).
But YES ... By all means ! ... This is a wonderful time and a good opportunity to install Win7-64 and a better GPU wouldn't hurt a darned thing.
In the process of swapping cases, be certain to also reseat all RAM modules firmly.
Check that the CPU is firmly/snugly "intact" but DO NOT attempt to remove or reseat the CPU/COOLER unless you notice a problem.
Do remove and re-connect ALL cards, RAM, power and data and signal cables and wires, etc., if you decide to do an upgrade, rebuild.
(AND, EVEN IF YOU DON'T)
You can show her what a stud you are and she can give you a big reward ... and ... a very fun date ... quality time, ... opining with authority!
... I'm just bustin' your chops ... I cannot afford a GF (on so many levels).
As everyone else says, play around and find the problem. My wifes computer started randomly crashing, had big fears the HDD was dying. Opened up the computer, turned out a fat wad of dust had managed to get itself wedged between where the SATA cable connected to the HDD which was causing the connection to sometimes 'break'. With that cleaned off it works perfectly again.
So, yeah, like everyone says, open up, clean out and reseat.
Completely pull the 9800 out of it's slot and remove the power connector ... Waive it three times, over your head, Place it firmly back, in the slot and re-connect (different?) pwr connector .... Fire it UP !
... Otherwise ... remove each RAM module (don't just push down) ... RE-insert each RAM module ... and .... Fire it UP !
Go to nVidia's official site and update your drivers ....
Alvin's list is a good one; there's not much if anything to add that wouldn't be self-evident as you examine the case. If there is a lot of dust, use a pressurized duster, not a vacuum cleaner, to remove it. Typical household vacuum cleaners can create a lot of static from the friction of dust on their hose walls.