Are you running out of hard drive space or want to upgrade to a faster hard drive? Acronis Migrate Easy makes it easy. I have used this twice before and it has worked excellent.
1.) Buy a new drive. I recommended getting the fastest RPM you can afford. Even moving from 4200 to 5400 RPM is quite a performance boost. Even better, see if you can get a flash based drive. Expensive, but quiet and lightning fast.
2.) Buy a hard drive enclosure if you don't already have one. You can then use this to migrate the data using Migrate Easy.
3.) Pick up a copy of Acronis Migrate Easy. Move your data over and swap the drive. Don't forget to format your old drive once you are sure everything has been moved over.
Acronis Migrate Easy
Froogle - External Hard Drive Enclosures