You uninstall the usual Windows way...

Start - Control Panel - Programs and Features (Apps and Features on win10)
click PianoCheetah
click Uninstall

Note that this will delete the WHOLE PianoCheetah directory including it's midi files, .WAV sample files, recorded songs, etc, etc.

But thank you for trying out PianoCheetah !!
It'll improve over time, so please try it again some day.