You're on the right track. However, with Vue Pro, there are no hidden files, nor are their any registry entries (except the path to the program) (unlike Vue 4). The files that are used for verification (in Windows) are vuepro.reg located in C:/windows, and Vue4Pro.eon, located in the program folder. Like thomllama suggested, "if" you have a legitimate copy, completely uninstalling the program, deleting the vuepro.reg file and removing the entire install folder (you can move your objects, materials, and other add-ons to another folder, then move back after re-install), and then doing a reinstall of the program will usually solve your crashing problem. Every time you open Vue Pro, Vue4Pro.eon checks your vuepro.reg file for any invalid serial numbers and if it finds one, it will trigger the crashes. It's also possible that you made a typo when entering the serial and the program is not recognizing it as valid. (you can open vuepro.reg in notepad to verify). I've also found that sometimes you can simply delete the vuepro.reg file, and when you attempt to open Vue again, it will ask for the serial number and once you enter the correct one, it will make a new vuepro.reg file. Hope this helps.