A program called "CompactPro" will extract .cpt files for you.
http://www.cyclos.com/compactpro.htm
Note that the installer for CompactPro will not run in classic mode. You will need to run this on a computer booted form Mac OS 9 or older, or run it within Basilisk II or SheepShaver.
edit
Actually I just tried it and StuffIt Expander 11.0.1 was able to expand it completely all the way to the control panel. I'm not going to redistribute software here, but do try this version of StuffIt Expander and/or CompactPro. Worst case, send me a PM with your e-mail address if you absolutely can't expand it and I'll recompress the control panel for you into just a .SIT file or something.
http://www.cyclos.com/compactpro.htm
Note that the installer for CompactPro will not run in classic mode. You will need to run this on a computer booted form Mac OS 9 or older, or run it within Basilisk II or SheepShaver.
edit
Actually I just tried it and StuffIt Expander 11.0.1 was able to expand it completely all the way to the control panel. I'm not going to redistribute software here, but do try this version of StuffIt Expander and/or CompactPro. Worst case, send me a PM with your e-mail address if you absolutely can't expand it and I'll recompress the control panel for you into just a .SIT file or something.