What JUCHECK.EXE does is on the 16th day of every month at 02:00, it checks for updates. If you wish to disable it, from the control panel, select programs/Java. Select the update tab and uncheck check for updates automatically. Same as on XP.
The strange thing about it is if you are an admin user, this works fine. If you are a non admin user, after a while, it switches itself back on.