Oh, the million-dollar question. Theoretically, Vista has an option to run software as though it were XP. If you right-click on the shortcut (whether on the desktop, in the Taskbar, or in the Start Menu) and select "Properties," you will see a window that has an option to "Run in compatibility mode." This has allowed me to run some programs that previously would not run in Vista. However, it has been my experience that these programs are highly unstable and tend to crash about 2-3 times an hour.
This issue is a primary concern of Vista's Service Pack 1, so we should see a fix pretty soon. If you want, you can try the release candidate (beta version) here
. It merits warning, however, that the patch may cause damage to your computer, as is strongly implied by this warning taken from Microsoft's website:
Microsoft does not recommend installing this software on primary or mission critical systems.
I myself have chosen not to download it as my primary computer is the only one with Vista. My backup uses XP Pro. SP1 is scheduled for release "first quarter 2008," so I hope we see it in the next couple of months.