To allocate more disk space for archiving restore points
Open System Properties
Select a drive from the Available drives box by clicking it, and then click Settings. If you have only one drive or partition, it is selected for you.
In the Drive <drive:>settings box, move the Disk space to use slider to change the disk space allocation for System Restore. Note that you cannot exceed 12 percent of the available disk space.
To open System Properties, click Start, click Control Panel, click Performance and Maintenance, and then click System. In the System Properties dialog box, click the System Restore tab.
System Restore requires at least 200 MB of available space on the hard disk (or the partition that contains your operating system folder). For best performance and protection, you should allocate more space.
By default, when the operating system installs System Restore on your computer, it allocates approximately 12 percent of the available disk space to System Restore to archive restore points.