Sounds like you're running into this problem. Before you do a system restore, would you look at a few simpler things?

First, open Regedit and look at HKEY_USERS. Is there a key named PE_C_User1? If so, that's why your User1 profile (or "registry hive") isn't loading when you log on. If Spybot is currently running, that key will be keeping your User1 profile in use. If Spybot isn't running, that key was left loaded by mistake. If you're familiar with editing the registry, you can unload that key. With luck, you can then log on to User1 and see your old profile again.

If your old User1 profile is still lost, look at this post for information about how to reset your profile path.

Finally, just for information's sake, is Spybot in your startup processes after a reboot? As far as I know, nobody's yet figured out how user profiles are staying locked through a machine reboot--the HKEY_USERS tree is supposed to be dynamically built for each Windows session.

Hope this helps,
Jay