Help Me!!!! S.O.S

well it started like this so i was playing some games then my computer crashed with some freaky colors so i have to cut the power manually i turned it on everything fine a few weeks later the same thing happened but this time there was an effect my screen was covered in weird colors i was like wtf weird green lines so i was like i can live with that oh and did i mention my resolution changed stuck on small so i went to go play roblox again the game i was playing when i crashed the 2nd time it said me graphics something to old i did some research and checked my device manager my graphics card or what i thought driver was wrong so i updated restarted the colors were gone checked my device manager everything going dandy went to play roblox again it went to the game then 8 mins later back to the drawing board aka it color crashed again and im back to it not working again so 1month and a half bought me some thermal paste im not a pc guy so i don't know wtf i did i got the video card out of the pc unscrewed it washed off the thermal paste with water yea i did i bet u looking at me like im stupid but i didn't have any rubbing alcohol used regular sink water put it on a paper towel and wiped all thermal paste off til i think it was clear then i reapplied thermal paste the kind i used was Ceramique 2 Tri-Linear Ceramic Thermal Compound put a small but not to small dot in the center of the card then put everything back exactly like it was hooked it back up to the pc it didn't work i raged and week later i go on the pc for about 1 hr i noticed the lines weren't there it was fixed played some games had a joly time but i color crashed once again but turned it back on going good then after that day i played a game and it crashed with the weird colors again -_- then back to the drawing board i just did some random shit to get the colors off my screen again i tried to do some shit to figure out whats up with my graphics card but it color crashed again now i'm back to square one again that was the last time i got a chance to see sweet freedom so am i screwed did i mess it up more than it already has already been messed up straight to the point , buy another graphics card i really don't want to or i can fix this somehow? if i can i'd be great here is some info on my stuff down below good luck on solving my problem p.s don't know if this info u need but what ever


Graphics card: Nvidia Geforce 8800 GTS 512 Gpu:G92 Release date: Dec 11 , 2007 Gpu clock 0 mhz memory 0 mhz
tell me if u know what i need to to do also tell me if u need more info