Of course could cause problems, anything could in a M$ program But i am always using different language type of dll, sys, and ini files (english, and hungarian). As I know only the language is the different in these files, so the only thing which could happen, is I will get some messages in english instead of hungarian. Using English SP on my Hungarian Win98SE is the same than using any other english hotfixes, system files right? But please correct me if I am wrong.