If you've really wracked your brain and still can't recall what it might be, a last resort is to go in search of a password cracking program such as The Password Recovery Kit or Advanced Zip Password Recovery. Shareware versions of which can be downloaded from their respective home pages.
These applications operate by bombarding the archive file, using a database of potential passwords, at speeds of up to thousands of times a minute. This may sound impressive on the surface, although in my experience, even at these speeds, such tools can be very inefficient and time consuming seeing as a typical password can be anywhere up to 30-ish characters long. Do the maths and you'll see what I mean!
These applications operate by bombarding the archive file, using a database of potential passwords, at speeds of up to thousands of times a minute. This may sound impressive on the surface, although in my experience, even at these speeds, such tools can be very inefficient and time consuming seeing as a typical password can be anywhere up to 30-ish characters long. Do the maths and you'll see what I mean!