If you install Windows Vista by upgrading an existing version of Windows, Vista does this by creating a copy of your existing files and keeping them in an alternate location on the new OS. Of course, you will want to move these files to the new location for your active Windows installation, so here are some Microsoft articles which may help:

• How to retrieve files from an earlier version of Windows in Windows Vista
• How to move Internet Explorer favorites from an earlier version of Windows to the Internet Explorer Favorites folder in Windows Vista
• How to remove the Windows.old folder that is generated when you perform a custom installation of Windows Vista

Overall, the upgrade is pretty painless, so hopefully these articles can save you a bit of time.