Scandisk was actually replaced in Windows XP with chkdsk (checkdisk), which can be launched by pressing Windows + R and typing in chkdsk /f (note the space). It will alert you that the disk is in use, which is normal...just type Y and press enter. It will run the next time you restart the computer.
Hope this helps,
It does not seem to work the same as XP--can someone tell me how to scan the drive for errors with Vista?