You've waited a little late in the game, but anyhow...What should I do if I'm running the Release Candidate (RC) version of Windows 7?
If you want, you could potentially create another partition, and copy your data (documents, music, photos, etc.) to this new partition (you will have to reinstall all your programs, you can't save them as is). Then, after a clean install of whatever operating system you choose (you didn't say, so I can only assume that you will buy the full Windows 7), you can simply copy the files back. Just be careful during the clean installation to not mess with your new data partition.
I personally would go with an external source of backup (external hard drive, etc.), but it is possible to do it with the same drive by just copying your data to a separate partition, then copying back after the install.
Does that make sense?