This is the way I'd do it:
1. locate the eMule folder in c:\program files and delete it. If it will not delete, go into the folder and delete each file one by one until you find the one or more file that is locked (this would stop you deleting the folder wholesale).
2. Download the freeware Unlocker from
http://ccollomb.free.fr/unlocker/ and use this to unlock the file(s), then delete them/it.
3. Download the freeware Regcleaner 4.3 from
http://fileforum.betanews.com/detail/RegCleaner/963771680/1 and on the
software tab look for any eMule entries in either column (you can sort them alphabetically). Tick and remove them.
4. Then, still in Regcleaner, click the
uninstall menu tab and remove any eMule entry there.
5. Then, still in Regcleaner, click the
startup list tab and remove any eMule entry there.
WARNING: Don't get carried away with Regcleaner and start removing other stuff!
6. Optionally (to tidy up) you could search your C drive using Windows for other eMule folders and delete them. There may be some in c:\documents and settings\[your user name]\application data.
There may be other tools that do all this automatically for you, but I don't know of any that are freeware.
Good luck!