The above answers certainly are correct. Just 2 additional notes.
1. If you have a good backup of all data you don't want to lose (and who doesn't?) you can use that as a source to populate your Windows 7 data also.
2. If you leave the current drive in the PC and load Windows 7 on a new one, there's no need at all to move anything. Just use the data as they are where they are.