Vista - instalation doesnt work

im using the 64 version. i have tried both booting up and running the
setup.exe file and neither works. when i boot it, it goes to the loading
screen and it will get all the way across and just freeze up, sometimes if i
leave it alone long enough i can come back and the screen will be
multicolored and pixelated. when i run the setup.exe file it just hangs on
"please wait" forever. my computer should be compatable. i ahve tried a dvd
and mounting hte iso.

i am running an amd athlon 3500+ dual core
1 gig pc3200 ram
nvidia 6800 gt oc video card
im trying to put it on my old 20gig hard drive