Did you check to see if the program is listed on the Control Panel's ADD OR REMOVE PROGRAMS? If you haven't checked:
START > CONTROL PANEL >
ADD or REMOVE PROGRAMS >
Look for this program and click to uninstall/remove it.
Note: Sometimes a program doesn't appear on the Add and Remove panel (regardless of when it was installed). In that case, click START > right click EXPLORER>PROGRAMS (usually under C) > locate the program and look for a file that looks like UNINSTALL or an abbreviation of uninstall. Click to run the file.
IF (and only if) the program doesn't appear on the Control Panel subset, and you can't find an UNINSTALL file through Explorer, you can try START > RUN > regedt32 (type it in), and do a search for all of this program's entries by drilling down each main category, searching for WMP 11 or abbreviations thereof. Delete all entries you find for the program - preferrably the entire folder if it shows up in regedt32. (Be aware that there are sometimes hidden program-related files, though, that only Microsoft could find.)
BUT BEFORE YOU TOUCH YOUR REGISTRY: Set a restore point. Go to START > ALL PROGRAMS > ACCESSORIES > SYSTEM TOOLS > SYSTEM RESTORE > SET A RESTORE POINT. Then if you blow it with regedt32, you can restore things without losing any of your data files that you have been working on or your email. I rarely have problems deleting from regedt32 unless I get 'trigger happy' and click the wrong thing! But just to be safe, set a restore point first. Good luck! And, p.s. - I don't recommend deleting a program's folder through explorer as a way to uninstall it. It rarely works, and sometimes prevents you from being able to get rid of it. :-)