You can boot from the system installation disk by inserting the disk and restarting holding down the "C" key. You will need to go to the second page pull down menu to Utilities -> Disk Utility and format the drive. You can then install the system. If you need to access your old hard drive for the data let me know and i can give you instructions for how to do that.

If you have a little HDD storage case (very cheap to buy) you can connect you new HDD to your current rig then run Disk Utility format and then go to 'restore'. There you can drag your old HDD icon to the "FROM" box and the icon for your new HDD to the "TO" box and hit enter. About 4 hours later if you are using a USB cable you will have a copy of your old HDD. All you need do them is follow the instructions to switch HDD's. If your old one is still working Ok you can put it in the storage case and use it for backup.

What happen when you shouce to boot from cd and shot down and retar agin like is goint to do something and just state in a gray screen