Put the recovery CD into the DVD drive and restart your G1S. As soon as the ASUS logo appears, press ESC key (be quick) and select DVD drive to boot your computer. The recovery procedure will start. Follow the instructions. You will be able to restore your G1S back to the original factory settings (just like a brand new one).
It will take about 2 to 3 hours. You must be patient during the procedure. Sometimes, it will look like it hangs (or freezes) there. In fact, it is still continuing. The computer will power off itself automatically when the recovery is completed.