1. Right-click drive C and select Properties.

2. In the pop-up properties window, click the "Disk Cleanup" button.

3. In the disk cleaning window that pops up (there will be a "calculation" window for a few seconds), click the "Clean System Files" button.

4. The "service pack backup file" will be listed in the disk cleaning entry (the machine has been cleaned, so 0 bytes will be displayed, usually in GB). Select the current check box for this item, and then click OK.

5. Click Delete File in the pop-up dialog box.

6. After cleaning, restart the computer.