I'm assuming you have windows freshly installed on your 160GB drive. If not, then install it.
You need to connect your 80 gig drive as a slave (using jumpers) or you can change the hard drive boot priority in the BIOS so the SATA is first (if you have the option to). Either way, the computer should boot from the 160 gig drive. Once it boots and loads Windows, just copy whatever files you need. It may take a while, depending on how much you need to transfer.