As per above, running under XP compat mode in Vista will address most of the common compatibility issues.
you could also try using the app compat toolkit (ACT) to create a shim to get the app working - it's pretty straightforward.
I've been involved in a number of corporate Vista deployments over the past few months and we've only had 1 app which would flat not work - that was resolved by running it in Virtual PC. not the most user-friendly approach but only a handful of people needed
to run it anyway...