I would login with the Administrator account or a temporary one with equal rights then simply rename those corrupt profile names under C:\Documents and Settings so you can re-create those accounts with the original names and if you need any program settings or data you can easily transfer from the renamed (unused) accounts.

When you are certain that you no longer need the renamed accounts, you can delete them but I would not rush into that till you are 100% certain, especially if keeping the old, renamed user profiles is not causing any problems.

Future reference, before doing any kind of registry, system or network tweak (system and network tweak are basically a type of registry tweak anyhow), run a registry backup. There are many free and easy to use tools to do that which is what Windows System Restore is, a glorified registry backup/restore tool.

My recommendation for registry backup/restore/defrag would be ERUNT.