To schedule Disk Cleanup in Vista:
Click Control Panel -> click System and Maintenance, to Administrative Tools ->
Task Scheduler -> click the Action menu, and Create Basic Task - create a name for new task click next -> select a schedule -> click next -> click Start a program and click next -> Type cleanmgr.exe in the File name box and click Open -> click next & finish.
Click Control Panel -> click System and Maintenance, to Administrative Tools ->
Task Scheduler -> click the Action menu, and Create Basic Task - create a name for new task click next -> select a schedule -> click next -> click Start a program and click next -> Type cleanmgr.exe in the File name box and click Open -> click next & finish.