A Qtek 9100 should have more than enough space to install our software - are you sure it didn't? What drive did PlecoCheck tell you install the data files to? PlecoCheck is very generous with its memory calculations, it assumes PlecoDict will take up way more space than it actually does, so if it says there's enough memory there really should be enough memory.
One workaround you can try is to install PlecoDict's components one-at-a-time instead of all at once; that will reduce the amount of extra memory that PlecoDict takes up while it's installing. Run PlecoCheck again and check to see exactly which drive it tells you to install files to; write that down, then go to Start \ Settings \ Remove Programs and uninstall any PlecoDict components that are already installed.
After that, run the PlecoDict installer again, and select ONLY the "ABC Dictionary" component - leave all the others unchecked. Finish the install, wait for the file to copy over to your Pocket PC, and when prompted about where you want to install the file, choose the drive recommended by PlecoCheck. After that finishes, repeat this process with the "NWP Dicitonary" component, than the "Oxford E&C Dictionary" one, then the font ("Demo Font" if you're running the demo version, "SimSun Minimal Font" if the paid one), and finally the "PlecoDict Engine". If you do them one-at-a-time and in that order you should have no trouble fitting all of the files into your Qtek's memory.