What does “Cannot Open the File: mk:@MSITStore” mean? 57

Windows XP’s help system has suddenly stopped working. Attempts to open a help topic give you the error message “Cannot Open the File: mk:@MSITStore”. What can you do?

So…less than two months of usage on my new computer and Windows XP Home edition is already starting to self-destruct.

I noticed that the Windows Help system failed to function most of the time. If requested, Windows would occasionally bring up a help file. However, in most cases it would give me a quick hourglass cursor, and then offer no further response (save the barely audible, gloating chuckle deep in the bowels of the computer).

After a worthless hour-long chat session with my Computer Vendor’s support (he recommended re-installing Windows XP) I decided the only recourse I had was to ignore the problem. After all, those Windows Help files are pretty useless anyhow. Right?

Two months later…I installed some new software and, it turns out, this new software uses Windows’ help system as an integral part of its interface. Specifically, it uses the Windows HTML help engine, which is designed to process .CHM (compiled HTML help) files.

Without CHM processing, my new software wasn’t gonna work.

Now, I’ve spent several hours trying to figure out how to repair this. Of course the Knowledge Base on Microsoft.com offered no knowledge. I did have one unexpected close shave. Searching for the error message “Cannot Open the File: mk:@MSITStore” returned one article that described my problem pretty exactly. However, the article was for Windows 98 and the prescribed steps couldn’t be completed in XP (where “regsrv” is apparently meaningless).

More time was spent copying files I felt were important (windows/hh.exe, windows/hhctrl.ocx, etc.) from my backup computer to the new computer. This still didn’t fix things.

Finally, I stumbled on this advice on Usenet. It fixed my problem and got things working for me again. I pass this tip in case this issue frustrates you too:

1) Use MJ’s Help Diagnostics to ensure that all the help viewer components are properly installed and registered.


(This turned out to be key as the software discovered the ocx file I’d copied wasn’t “registered” and did that for me.)

2) Delete the file “hh.dat”, which you should find in this subdirectory:

\Documents and Settings\%username%\Application Data\Microsoft\HTML Help

This file stores information about all the HTML Help files on your system (Favorites, window size and position, etc.), and can cause the files to misbehave if it has somehow been corrupted.

I actually did the second step first and it didn’t ultimately solve the problem. It might have if I hadn’t copied the OCX file from the backup system first.

So there you are. Hopefully this will help some frustrated Windows XP user out there solve things faster than I can.

Next PC is a Mac.

57 thoughts on “What does “Cannot Open the File: mk:@MSITStore” mean?

  • Haseeb

    Wow wonderful, I was really annoyed becasue of this problem, and hardly was able to find any good solution,…. and finally this one worked,… Great Help Dude..!!

  • Robert June

    Hi I have a question I’m not sure if I bought coolpro2

    from your company. I have lost my cool edit program.

    Long story lost my house back in 08 and put stuff in storage

    lost every thing in storage. the only item I still have is the

    User Manual. I have a license NO. at the top 210-10-NMl46R4c .

    I Found a Q&A sheet from your website. That’s why I,m thinking

    I bought My cooledit from your company. the date at the bottom of

    your info sheet is 9/8/2004. If I Did Buy from you back in 2004

    what would that program cost me today/

    Thanks Bob June

  • TAkr

    I’ve had this problem for more than two years. It appeared shortly after I bought my current computer. I did try to solve the problem back then but I just wasted many precious hours. This solution worked like magic! Incidentally, it worked just by using Step 1 (didn’t need to delete hh.dat). Thanks Rob!

  • nonexist

    don’t use chars like [ and { in directory and file name
    that’s all
    SOLVED for me;
    If directory name has characters like {[
    “Cannot open the file: mk:@MSITStore”
    I moved the files to another directory and all them worked

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