The app that comes with Java and is responsible for scheduled update checks is called jucheck.exe. Not jukcheck.exe, not justcheck.exe, not anything else. If the name looks iffy, don't run the file or let it make any changes. The file is very likely to be a malware made to look like a Java updater.
Fire up msconfig (Start menu -> Run -> Type msconfig), switch over to the Autorun tab, and uncheck the box next to the dubious file. Then run a virus scan.