You can buy a later version of Nero that will run under Vista. If you bought a retail copy of Nero 6 and still have something that proves it, you might be able to upgrade to a later version for a reduced price if the company has that kind of offer.
Another option, the one I suggest, is to uninstall Nero and replace it with CDBurnerXP
. It's a completely free burning program that offers CD and DVD burning capability, makes audio CDs, copies discs, etc. But the best feature is that it's free, and it will run on Vista systems. You just need to have Microsoft's dot-net framework installed, but that's on many computers already. If not, it's available from Microsoft's update site at no charge.