For the former:
Go to Start/Run/Regedit and verify this key and values:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\ Explorer\My
Computer\NameSpace\DelegateFolders
Sub-key named {59031a47-3f72-44a7-89c5-5595fe6b30ee}. If this subkey is not
present, you will not have the group: Other files stored on this computer.
Other than that, if you are using TweakUI check your settings under - My
Computer/Files stored on this computer. And/or run the edit on line 56:
http://www.kellys-korner-xp.com/xp_tweaks.htm
Added info:
To get an account's My Documents folder to appear in Windows Explorer (Files
stored on this computer), add/edit a key in the DocFolderPaths branch like
so:
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\DocFolderPaths]
"user"="C:\Documents and Settings\user\My Documents"
In the right pane, right click and choose New/String Value. Give it the
name of the user. Double click the name once added and type in:
C:\Documents and Settings\[User Name]\My Documents