To access System Restore select Start --> Accessories --> System Tools --> System Restore.

Click on the, Undo my last restoration, and click Next.

The Confirmation window will appear which asks you if you want to undo the last System Restore.

The computer will then restart and undo the last system restoration perofrmed.

Once that is completed the Undo Complete window will appear, if you are satisfied with the undo of the last system click on OK.

If you are not satisfied then repeat the System Restore steps.