For the backup feature built into Vista you can go Control Panel->System and Maintenance->Backup and Restore Center->Change Settings->Turn Off.
However, PC manufacturers often bundle their own, as do internet security suites now, so it may be a third-party application 'at fault.'
John
When I boot up vista it tells me to remove unused programs every time. Also it tells me to back up my programs but when I try to it tells me I have no space left. I don't want to back up, how can I turn this off.

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