Vista 64 - possible graphics card problem?

[thisisgazza]

Hi Everyone, just wanted a little advice before i start spending some money.

The problem
when i drag windows across the screen, i seem to get a bit of screen lag/shadow. Naturally i thought the graphics card was the problem. So i installed it on another computer (windows 7). It sempt to be working ok on there, possibly a minor lag, but nothing compared to my other computer. Maybe it was because its window 7 it may work a little different.

I have reinstalled my computer and installed the latest drivers and still have the problem. Ive tried benchmark programs and it seems to be working fine. Ive not had any problems like this before so wouldnt mind a little advice and how i can find out the problem. Are there any programs that could diagnose the problem?

Specs;
Windows Vista 64 - all updates done
4GB (2x2GB) Corsair XMS3 DDR3 PC3-1
Gigabyte GA-790XTA-UD4 motherboard
OCZ Z Series 650W PSU - 80plus Silver
AMD Phenom II X4 955 Black Edition 3.2 GHz Socket AM3 8MB
GEFORCE 9800GT SLI 512MB DDR3

Thanks for your help

Andy

 

[Bane]

What display are you using?

 

[thisisgazza]

Hi, thanks for the response.
do you mean monitor?

If so, i have them split to 2 different screens. If im watching DVDs etc then i have it on my Samsung tv (1024 x 768) VGA, if im doing work then i transfer screens to my office Viewsonic monitor via HDMI (1920 x 1080).
Ive been using this method for probably over a year now without any glitches, so would assume this isnt of any problem.

Any ideas anyone?

Andy