Click Start, point to Find, click Files or Folders type mapi32.dll, right-click the file and then click Properties. Check to see if the Read-Only check box is selected. If it is, untick it.
Next go to run and type Fixmapi.exe and hit enter. If this fails then go to the windows\sendto folder you should have a zero byte file named Mail
> Recipient.MAPIMail do you? if not you will have to add this file.
Open the reg and go to HKEY_CLASSES_ROOT\.MAPIMail is it there and what is the value?
If you don't want to write a reg file the you could try downloading the mapistub.dll from click here and save it ti windows/system.