Boy, that's a tough one.
There are some applications that use a *.zpk file format, including Zcapture, and the Z-Firm system. A function called "zpkin" might be related to this file type.
Other than that, I'm stumped. What does the "properties" function tell you about these files? You must be using Win XP since I don't think any others use the "prefetch" function.
