Update function for content of existing CD?

Hello all. I am looking for some ideas on how to design / structure a script which checks for updates on files on a existing CD ROM. Every week, I generate content for a CD ROM containing a large number of html pages and PDF files (the CD is distributed to 20 - 30 dealers for ours) . The PHP script which is doing this is outputting a ZIP compressed archive. This ZIP file is then unpacked and burned on a CD. I am now playing with the idea to provide a "check-for-updates" function on the CD. Because the ZIP archives are rather large in size (300 MB), I am not able to keep all ZIP files. One or two months back is ok. My idea is to have a db table on MySQL containing checksums for all files of the archive and have a script that is able to compare those lists. (one ZIP archive has about 400 - 500 files) My idea is: On the CD's start page I could have a link like: http://myserver.com/look_for_updates.php?myArchiveName=2006-11-10 The script will then compare checksums for the files included in the archive "2006-11-10" and checksums for the recent file list. It then outputs a new ZIP file including new and updated files. Do you think that there is another (more elegant) way for doing this? Keep in mind that a ZIP file contains about 400-500 files which means that the table would grow rapidly week by week. In only one year the table would contain roughly 25000 rows of data. /frank