You can disabled backup per the below:
Open OneCare
Click Change Settings
backup tab
Click Configure Backup
Click change settings in the lower left
Make sure that the first screen for Centralized Backup has "No Centralized backup" selected
Click your PC on the left.
Uncheck the selection for "Turn on backup for this PC."
Click Next and save the revised plan.
Or, change the frequency of your backup. If you do wish to use OneCare backup, it will be yellow until you complete the scheduled backup.
-steve