As Windows Vista features some fundamental changes to the way the operating system works, some older applications may not function properly under Vista. To help get around this snag, the Microsoft developers have included the ability to set compatibility settings on a per application basis. This may allow you to run programs that otherwise would not load properly.
To do this, right click on the main application file and click Properties.
Then, click on the Compatibility tab at the top of the window. You can then tick the "Run this program in compatibility mode for..." box and choose the operating system the application is designed to run under (i.e. Windows XP). You can also choose any other options, such as running at a reduced resolution, then click OK.
Hopefully this will then let you run the application, but you may need to try several compatibility settings to find which works best for a troublesome application.