Reinstalling windows 7 and ownership of user data on different drive

Hi, I keep all my data on a separate drive. The last time I re-installed windows 7 I had to take ownership of all my data even though the user name on the old install and then new install was the same. After reading the forums I understood that the SID for my user name was different between the old and new installations. So my questions are 1) Is there anyway to assign the old user SID...