Is it possible to run different releases of CCD on the same PC?
Yes. Just make sure you install the new release/update to a different directory. Then use the Ccdraft\Bin\ccdver.exe utility to switch between releases. Note however that some combinations may not work. For example, if you use 424 and you activate the new Macro Toolbar, you will no longer be able to run previous releases of CCD on the same machine because previous releases will not know how to handle this new toolbar setting.