If you know where your active User files are, then copy their folders (Documents, Downloads, Pictures, Videos, etc) over by dragging folder from C:User folder onto External.
If you are afraid you'll leave something out, then copy the active User file which will carry everything with it.
Make your Vista Factory Recovery Disks so you have a path back to factory condition in case you ever want to sell your computer but keep Windows 7.
Gather your program installers, boot the Windows 7 DVD, select Custom install, use Drive tools to delete all partitions, create New one(s) as you wish, then format before installing Windows 7 to first partition. The installer will scan the HD at bootup to see Vista and allow use of the Upgrade version key.
The installer is driver
-complete, with newer arriving quickly via Windows Updates. Any drivers
missing in device Manager or favorite apps can be found on the Support Downloads webpage for your model computer or device, Adobe (flash, Reader), Java (Runtime, free Ofc suite) sites.
Suggest you install Programs gradually with time in between to gauge performance changes. Make sure no programs add themselves to msconfig>Startup tab unless they absolutely need to start up with computer as these become full-time free riders on your RAM/CPU and affect performance - only your AV (suggest free MS Security essentials for lightweight effective AV) and sidebar gadgets need to startup really.
After programs and Updates are installed, clean and order HD using state-of-the-art CCleaner "Run Cleaner" and Registry tab, and the Auslogics Disk and Registry defraggers, then use them monthly to keep whistle clean and perfectly ordered.
Finally, save a Windows 7 backup image externally so you never have to reinstall again, just reimage the HD or a replacement in 20 minutes.