I notice from some of your other posts that your printer is a few years old. If you are installing from the disks that came with it, that is likely VersaWorks 2.xx. You will need at least 3.xx to install on a Vista system, and Versaworks is currently up to 4.xx.
I am guessing you can't do an update, since VersaWorks isn't even installing, but if you give Roland tech support a call at (800) 542-2307 x2, they will be able to help.