I couldn't find this posted before.
I found this Registry entry to add Register and UnRegister to the right click context menu. Copy and paste the following into notepad and save as whateveryouwant.reg. Find the file in Windows Explorer right click and merge. Click OK and alls done. I know this works with Windows7 and Vista. I don't have XP to test it. Must be exactly as shown. If this key doesn't work with XP I think where the key says "Version 5.00" change that to "Version 4.00"
Windows Registry Editor Version 5.00
@="regsvr32.exe /u \\\"%1\\\""