How about copying the profile of the user...
Create a new account with the username the way you want it to appear,
and be used for networking and the like, then copy the old user profile.
Open System in Control Panel. On the User Profiles tab, and under
Profiles stored on this computer, click the user profile you want to
copy, and then click Copy To.
In the Copy To dialog box, under Copy profile to, type the location for
the new profile, or click Browse to select the path.
Click Change to open the Choose User dialog box, click a new user from
the Names list, and then click Add. The new user name will appear in Add
Name. Click OK to add the user as a new user profile on your computer.