Defragments your hard disk
Personal computers tend to save changes to files to the largest continuous space on the hard disk, which can often be on a different sector than where the other parts of the file are stored. Over time your files can become "fragmented," which means that the computer must search the hard disk for all the parts each time you use the file. Excessive file fragmentation on the hard disk slows down your computer's response time, so it's a good idea to defragment your hard disk regularly.
Windows Live OneCare Tune-up finds and consolidates any fragmented files and folders on your computer's hard disk so that each file occupies a single connected space on the disk. As a result, your computer will be able to access your files and folders and save new ones more efficiently.
Frees up hard disk space
With an operating system as complex as Windows, you might not always know what all of the files on your computer are for. Sometimes Windows uses files for a specific purpose and then retains them in a folder designated for temporary files. Alternatively, you may have some previously installed Windows components that you are no longer using but which remain on your hard disk.
Windows Live OneCare Tune-up can locate and delete such unneeded files. Because this task involves deleting files from your computer, you must choose to turn on this option after you've installed Windows Live OneCare. Turning on this task can help reduce clutter on your hard disk, create more free space, and help improve the performance of your computer.
Scans for viruses
Tune-up also runs a full virus scan to check the files on your computer for viruses and other malicious programs. If an infected file is found, Tune-up helps prevent harm to your computer by automatically blocking the file until you decide what to do with it.
Note that this task scans files that are already on your computer. It's different from antivirus monitoring, which is an ongoing process that runs whenever your computer is turned on and checks your programs and files for viruses while you use them.
Tracks updates for Windows XP and other Microsoft programs
Tune-up also checks whether your installation of Windows XP is current with the latest software and security updates. Tune-up works with Microsoft Update to get your computer the latest updates from Microsoft.
Checks for backup (and backs up automatically if you use an external hard disk drive)
Tune-up checks your files and notifies you when there are new or changed files that need backing up. If you use an external hard disk drive for file backups, you can set Tune-up to back up your files for you automatically.