Is there an issue just at Control Panel - Add/Remove
programs (or I guess, it is called Programs and Features now)? Does it still
show there? If it does, then you just have to perform the procedure, similar to
described here:
look at the second section, about removing things from
uninstaller...
However, I did hear of couple of reports, that above
procedure does not actually remove entries, if you are using remote desktop, and
you are not connected via console session. To use console session for remote
desktop, go to DOS prompt and type
mstsc /v:computeraddress /f /console
and try to alter registry from there...
About the rest... You delete WebMail application from
IIS manager, and then physically get rid of files in the folder...