Prior to deleting Sound Forge Appdata files and uninstall/reinstall, you could try resetting Sound Forge and clearing the cache. which is normally executed in the 'File' menu.. "Reset all preferences and clear cached data". But since SF will not open, hold down the 'Ctrl+Shift' keys, and launch, which should open the tool w/o opening SF.

btw, instead of deleting the Appdata files manually, I usually recommend using a third-party uninstaller/cleaner like 'Revo Uninstall' that can remove the left-over registry entries and the other pertinent data that is left behind, doing a more thorough job. Revo Uninstall has a pro and freeware versions. The free version is adequate in most cases,