Video card troubles

[bf2nick]

Alright, I have a Dell Dimension 8400 (junky I know) well I recently acquired a Nvidia 6800GT from a friend to put into my computer to replace my ATI X300. When I booted up for the first time I got lines in my screen and I thought it was just a driver problem, so I installed the new drivers and nothing improved. So then I ran a driver clear program to get rid of any old existing drivers from ATI so I would not have a conflict. I inserted the 6800GT back into my computer and booted up and I had lines, but no drivers so I continued on to install drivers and everything got worse, I could no longer see the welcome/log on screen on XP for it was a bunch of lines. Everything is connected properly and I or any friends can not seem to figure out what is wrong. Also with the drivers installed my computer gets really slow and doesn't process hardly anything. I have tried drivers from two different places and I have no idea what the problem is can anyone offer some help please.

[luke992006]

since you took it out once then put it back in and it was worse it sound like it is not seating properly...try moving it around. Was the former video onboard..if so have u disabled it in the bios?