If you changed your Account user name & your old user name still shows using "My Computer"
user's/ Documents
Do a Search Advanced for old user name , ie:  TOM
& change Folder name TOM to "NewUserName" in;
C:\Documents and Settings\TOM

 

then use Regedit to navigate to HKEY
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList
& select HKEY below which shows;
"ProfileImagePath"       %SystemDrive%\Documents and Settings\TOM

& change to  %SystemDrive%\Documents and Settings\"NewUserName"   as above

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You could also create new Computer/Administrator account Logon with it & Delete your old Computer/Administrator account using "Save files".
This will save a Folder to Desktop called your old user name & contain "My Documents" of old user.
If you create a new Computer/Administrator account it will load a new Desktop.