You will need to log on with another account that has admin access. Then do the following.
Open regedit, and go to HKLM\software\Microsoft\windowsNT\currentversion\p rofilelist\
go through the guid reference names until you find the one that contains larry.Larry in the ProfileImagePath. That is the one you will want to edit. Then double click the ProfileImagePath value and change the refference to larry, by deleting the .Larry from the end. Then close regedit, and go to C:\documents and settings.
There you need to rename the folder called Larry.Larry to Larry
Reboot the box and have Larry log back in. That should do it for you.