Hi YT, and welcome to Sevenforums
Depends on how many times you want to do this
If you are building a slipstreamed install for many users then the Windows Automated Install Kit is the official method and should allow you to do this. Not sure if this is now at RTM level but I know that the WAIK is available for Windows 7 at least to Beta level on the Technet site.
If you are looking to make this system change on an Ad-Hoc basis It can be achieved by the use of junction points after the install You will need the Movefiles Utility form sysinternals as this is a system folder but the redirect should be totally transparent to the OS when complete