When you right-click My Computer icon in the Desktop and choose Properties, the Remote tab may be missing. As a result, you may be unable to configure the Remote Assistance / Remote Desktop settings.

To restore the tab, follow these steps:

• Click Start, Run and type this command:
  regsvr32 %systemroot%\system32\remotepg.dll
  If you receive an error stating that the module could not be found, or stating no registration helper is registered for this file type (which indicates a corrupt DLL), extracting a new copy from XP CD should help. Make sure that you extract the updated copy of the DLL file if you have applied the XP Service Pack in your system. Register the DLL again.

(Extract the DLL from a XP CD, or copy the remotepg.dll from ServicePackFiles\i386 folder to Windows\System32 folder)
To extract the DLL from Windows XP CD, type this in Command Prompt
EXPAND X:\I386\REMOTEPG.DL_ -R C:\WINDOWS\SYSTEM32

Where X:\ is your CD-ROM drive letter. The above command assumes Windows is installed in C:\ drive. If not, change the drive letter / Path accordingly.
Example: EXPAND H:\I386\REMOTEPG.DL_ -R G:\WINDOWS\SYSTEM32

See also: http://support.microsoft.com/kb/306300