You can install right over the top of the existing version. Usually there' no need to uninstall. That said, in Windows open Control Panel|Programs and Features to uninstall. Upgrades are not forced, but prompts may request a purchase.
Your "original" install file should have been stored in this path: "C:\Program Files (x86)\NCH Software\VideoPad" Simply double-click on it to reinstall. Be aware that some features will be disabled in the unlicensed copy after the trial ends.
The tech issues you mention have not been seen here. Please be more specific on the steps you are attempting when the freeze occurs and what VP version is being used.