If in windows explorer, you right click on a .mat file and then click on "properies", does the "opens with" line show "Microsoft Access"? If it does, I can see Access interfering if you try to open the file by double clicking it. Also, as mentioned in a post above, you should save the file (.mat or .zip) to disk, not use the "open with". Another thing you might check, using the Task Manager, see if there are any MS Office processes running. I don't remember the name, but I do remember using the program Starter by Codestuff's to disable several programs, and one had references to OfficeXP.