Here are some hints to upgrade your PC to Windows 7:
1. Download and run the Windows 7 Upgrade Advisor to see if your PC is ready for Windows 7.
2. Two key words:
- Upgrade: files and applications are maintained on the computer and do not need to be reinstalled. Available for some computers running Windows Vista only.
- Migration: clean installation, files and settings must be transferred to a safe location prior to installing. After the installation is complete, move the files and settings back and then reinstall.
- Open Windows Easy Transfer by clicking the Start button.
- Type Easy Transfer in the search box, and then click Windows Easy Transfer.
- Follow the instructions, then it is done.
Visit Installing Windows: Recommended Links, for more information.
Source: Microsoft/Windows/Windows 7.