- Go to http://www.hp.com/support/ and download the OS 9 PPD file, and unstuff it if necessary.
- Rewrap the PPD file using gzip, to end up with a file named HP2500C.PPD.gz.
- Copy this file to your system's PPD folder, located at /Library -> Printers -> PPDs -> Contents -> Resources -> lang.lproj' (replace lang with the language your system uses).
- Then add you printer in the print center using the 2500 PPD you just added (when choosing the PPD file choose 'Other...' and navigate to the location you copied the PPD file into).
[Editor's note: I did this quite a while ago with a Brother HL-1270N, and didn't bother placing the PPD anywhere special nor gzipping it; I just pointed to the raw PPD file when setting up the printer in Print Center, and it worked fine. This method should work for any printer with a PPD file...]

