Thunderbird not recognized by mailto in context menu

hello everyone
i'm running xp sp2 using mozilla thunderbird. when right clicking a file to send to mail recipient nothing happens. i have checked to make sure thunderbird is the default mail handler. if i switch the default to outlook express, everything seems to work fine.
this behavior started after removing some unneeded services, so i suspect that may have a bearing on the issue.
is there a particular service that controls this function? hopefully, the fix may be nothing more than reinstalling the service.
thank you. i appreciate any help you can offer
deck