i recently downloded VSTi instruments that i didnt know needed activation codes and now they're just in my list of VSTi instruments not able to be used.
Find where the VST instrument files you do not want are located, browse to the folder with Windows Explorer and move them to a folder before you finally delete them.
Studio should read the VST folder everytime it starts, so once they are moved then it does not read them.
When they are not in the list then delete the VST files you moved.