Click Start, point to All Programs, and then click Set Program Access and Defaults. . That should set you straight.
If that's no good (I'm doing this from memory as my boxes are all win7 now), have a look here:
Setting the Default Email Client in Windows XP
Now get with the 21st century & install win 7, ditch that bitter Arsene & come to the mighty 'Arry for without a path to enlightnement, that is far as I am prepared to assist a deluded Gooner.