Do you have an external hard drive. Before you do anything make a disc image of your Vista system drive and any other drive with important information on. That way you can always go back to square one.
Uprade Vista to Win 7 and make another system image. Have a short play by loading an existing project and check that P12 is working properly. Now arrange your files according to the way YOU want them. By that I mean the project, captured, render and output files. You do not need to use pinnacles default locations. Many people partition their drives so that the system drive is just that and remains fairly compact with system and program files. Your documents and project files would be in the 'D:' drive (partition) while the captured, render and output files go on a second hard disc. The actual arrangement, of course, depends on what YOU want.
When satisfied, do further disc image backups of the system and your data. Now you can play with Win 7 to your hearts content knowing if anything goes wrong (and it probably will) you have a fall back position.
Although it is a new computer, some of your software may not be. Visit here to check compatability issues
http://www.microsoft.com/windows/compatibility/windows-7/en-us/default.aspx
For any Win 7 problems the Technet forum is worth a visit
http://social.technet.microsoft.com/Forums/en-US/category/w7itpro
Some people have trouble, some don't.
Best of luck.