There's a problem with at least some versions of Vista installing when you have 4GB of RAM installed. In any case, before installing Vista, make sure your system is stable, since essentially all RAM sold these days as faster than DDR2-800 is really overclocked, requiring higher-than-standard voltages. This often causes problems on new installs, since the MB cannot automatically set the RAM voltage higher than the standard 1.8V.
Download and run memtest86+ (it's available as a bootable floppy or CD image file, which doesn't require an OS installed to run) and make sure there are no errors after at least two full passes.
I had only 2GB of RAM installed and I had setup the BIOS for this RAM by setting the freq. to 1066MHz and timings to 5-5-5-15-8 2T and raised the DRAM voltage to 2.20v which are the factory spec's and I set the NB to 1.31v. So I don't think it is the RAM. I have another computer I was putting together at the same time that did the same thing. I was trying to load XP Pro on it and got the same message. The two things these computers have in common are the SATA Optical drives, which by the way are different brands, and they both have ASUS motherboards.
I am at a loss and have sent ASUS a tech request. I think in the mean time I will try to load the OS using IDE Optical drives and see what happens.
Thx's Mondoman for your input and I will return when I have news to report.