1. Try another unzip program. There's a free one in XP, and many free ones (like 7Zip, Tugzip) can be downloaded.
2. Try this particular zip-file on another PC (via a USB-stick, for example).
If none work, the file is corrupted somehow. Then find the maker and ask for a better copy.
I have a zip file with 4 files inside. When I run Winzip only 3 of the files are extracted. I've tried extracting them individually and also as a group but with the same result. What does this mean for the file that can't be extracted and is there a fix for this problem?