Back up the important stuff you want to save, or you can shrink the partition using the Disk Manager windows provides. There really is no way to just migrate (copy) since you will run into many many many more issues due to reg entries, drivers, etc...
The way I would do it, Is copy the docs and files that contain the data you want to save on a pen drive or network location, then when installing your upgrade, blow away the partition that contains the RC and have Win 7 use the whole drive. Reinstall your apps, and migrate the data and information over to the new install.