Also, the wall moving around is most likely caused by the Vsync being turned off in your control panel.
Turning VSYNC off does improve FPS but causes those problems. Since your card is fairly low end, your FPS must be also fairly low which causes you to notice those distortions.
Note that by enabling VSYNC, you will lose FPS so if they are already low (choppy display) they'll get even worst.
here are a few tips:
increase your memory if possible
close any unnecessary programs running
defrag your disk
In your control panel, reduce your AA and ASFA to minimum (anti-aliasing and anisotropic filtering)
decrease the quality of the rendering effects in your game options
get latest ATI drivers
My gaming machine:
P4 2.8 GHz
2 X 512 MHz PC3200 in dual DDR mode
Intel D865PERL MOBO
integrated 6.1 MAX audio
Logitech duo MX mouse and KB
ATI RADEON 9800 PRO