Here's what you need to do:
1) Open the Vista Guest PC
2) From the CD icon in the bottom of the Guest PC window select the "Connect Image…" option, then navigate to /Library/Parallels/Tools/ and select the vmtools.iso file and click OK. This will "mount" the Parallels Tools disk
3) Click on the Windows icon in the start bar (What used to the be Start option in XP) On the right side of the list you'll see "Computer" Right click on this and select "Properties". This will take you to the System screen
4) Select the "Device Manager" option from the list of tasks.
5) To update the mouse driver, expand the "Mice and other pointing devices" item and double-click on the item within there, you'll see the Properties dialog for the Mouse, click on the Driver tab, then select "Update Driver". From the Search for driver window select the "Browse my computer for driver software" option, then navigate to the CD drive and select the Drivers folder on the CD and continue.
6) Repeat the above steps for the other drivers.
Reboot the computer and you should have all the drivers installed correctly.