NO NO NO NO...... listen. sending it back to toshiba will only cost you money, time and hastle. All they will do it back up (Make a Copy) of your important data. And put the Toshiba Recovery CD in and restore it to how it was when you bought it.
Now the walkthrough is exactly the same but the only difference is its VISTA.
Now the multiple NtUser.Dat are for each user account that you have. Now you said you have 3. Chances are they are for, Administrator Account, Guest Account (if Enabled) and your primary User Account. OR if you tried to delete them them vista will make another copy of the one you deleted and rename it EG... if you deleted NTuser.Bat Windows will most definatly create NTuser1.bat and probably NTuser2.bat as a backup.
Now as far as your laptop is concerned. the only worry you have is weather you can access your user accounts. if you can. its very simple. BACKUP ALL YOUR IMPORTANT STUFF. anyone will say it. its best to have a backup then to find out you have rubbed everything off. (I have done it, and believe me, it leaves a hole in your stomach.)
If you follow the instructions on the link until "PART 2" when it asks for the operating system you want to repair. If it gives you the choice, REPAIR IT.
this process will delete the Operating System (Just the OS) and reinstall it as if it were a New Install. You may have to reinstall you programs and updates but your data will be in My Documents.
DON'T DELETE IT AND DON'T INSTALL IT BECAUSE YOU WILL LOSE EVERYTHING ON YOU DISK.
This will most deffinatly help. If not PM me.