Restore old Exchange 2003 mailbox while running with Working Exchange 2010 Server

Hello,

I've migrated all my folders from the old exchange 2003 server to the NEW Exchange 2010 Server.

I had one user who claims to have lost a folder even though the migration logs show no problems?

I have a backup of the Exchange 2003 Information Store before the migration.  My question is.. Can I run through an

Exchange 2003 Mailbox Restore to a Recorvery Database on the old Exchange 2003 Server - without hurting the NEWLY created migrated mailbox in the Exchange 2010 server?

I just want to make sure that if I restore the old 2003 mailbox that it doesn't effect the new 2010 server mailbox for that user.  I can't see how it should be effected?  Just want to make sure before I begin the 2003 restore process.

Thanks.