Well, there's the rub - when I x2 click in explorer it opens in notepad++.[/url]
As Olaf says, your file associations in the registry are whacked. I cannot imagine Notepad++ doing this on its own. It is generally far better behaved, but that's neither here nor there.
Right click on the CHM file in Windows Explorer and choose "Open with...". In the resulting dialog, locate and choose "Microsoft(R) HTML Help Executable". (It *should* be on top of the list, but we've already established that your system defaults are a little whacked.) To make this change permanent, check the box that says "Always use the selected program to open this kind of file".
None of this has anything to do with Foxpro, of course. This is basic Windows behavior.