Changing your username would be much easier to just create the new name as a user and cut and paste all the files to the new directories once you have logged on to your new username. After all the data and files are moved, you can then log on to your new userid and remove the old one.
That would be a much simpler method.
(this is all assuming that each of them is an administrator)
Rich
My Computer
Computer type
Laptop
Computer Manufacturer/Model Number
Toshiba Laptop Qosimo X870
OS
Windows 7 Pro x64 SP1
CPU
Intel Core I7
Motherboard
Toshiba Qosmio
Memory
16 Gigs
Graphics Card(s)
NVIDIA GeForce GTX 670M
Monitor(s) Displays
17.7" laptop
Screen Resolution
1600 x 900
Hard Drives
256 Gig SanDisk SSD for C
256 Gig Intel SSD for D
Internet Speed
50/25 FIOS
Antivirus
Vipre (all you can eat for 10 machines)
Browser
IE and FF
Other Info
I have dos 6.22, wfwg 3.11, win98, 2000 and xp VHD's available for testing. MS's Virtual PC works great.