Perhaps it has happened to you as well to get a weird message while trying to open a help file under Windows 9x and even 2000/XP: "Cannot Open the File: Mk:@MSITStore: C:\Windows\Help\Windows.chm", here is how you can fix this problem.
Windows and errors
Although Windows XP is far less susceptible to errors than Windows 9x, it seems there are still some errors that remind me of that old operating system. One of them is an error you usually get when you uninstall a program.You install a small program for a random purpose, you like it or not and for some reason you uninstall it. You don't notice anything suspicious and after a couple of days (or perhaps the very next moment) you try to open a help file and notice a weird error message.
Although this is not very common, it has happened twice to myself and I've seen at least hundreds of complains about it over the Internet.
Some people would just reinstall the operating system and eventually get rid of this problem, yet there is also a much easier solution.
The hhctrl.ocx file
The problem is caused by the file hhctrl.ocx located in your System32 folder (or just System on some OS) and most likely has been overwritten by an application with an incompatible version.So, all you need to do is either look for it on the cabinet file from your Windows CD-ROM or download/copy a working version from an outside source (or even from a backup you might have made yourself). You can for example download a working version from: http://freeware.it-mate.co.uk/?Cat=OCX_Files
When you have it on your computer, just copy it into your c:\windows\system32\ folder (well, if your Windows directory is called otherwise, change it accordingly) and overwrite the old version.
Then, go to your start Menu and select Run:
regsvr32 c:\windows\system32\hhctrl.ocx
After that you should see a message that the file was registered successfully. Open a help file to see if it worked. If it didn't, try a different version of that file.
