Probably a key or save data and do a fresh install. You can probably get a key somewhere just for installation but it won't activate. Sorry, don't know much about uninstalling those site apps. Why is it so important, especially if your client had Pro before? It's really their problem unless they're willing to risk their data.
If I have a key I don't have to do a clean install. What do you mean with "save data"? No, just because I have Enterprise in the other PCs...
As posted by MrMagic and rpo (above) - no problems. Following the link in my post leads to a download of a zip file (WinXMenuEditorRelease.zip), extract it and it gives an x64 and x86 folder, and a ReadMe.txt - open appropriate folder and run WinXEditor.exe - no problems.
I would think if you had even just an installation key it would work to upgrade to Enterprise. If so it would probably tell you as much just before the install started. I meant if you did a fresh install you'd want to save their data first. Seems like a lot of work for not much--why don't you just give it back to them the way it is?
There were keys that I inserted which weren't valid. Of course I'd save their data first before doing a clean install. Well, that's what I think I'll do (keep the system as it is now)...