Put the drive that came with the pc back in and set it for master and make sure its hooked up on the end of cable, now take the sony drive and look at the back of it and you'll see some jumpers. Put the jumper on the pins for slave and hook the drive up to the connector in the middle of cable.

Ok now when you boot it should boot from the (orig. drive) master. Once inside windows you can access the sony drive (make note of drive #) and get the stuff off that you want to keep. Now go to My Computer and you will see the sony drive, right click and choose format. Choose what type of file system (NTFS or FAT) and do not ! put a check in quick format...let it do the long format cuz it will check for & fix bad sectors on HD.

When format is done just stay in windows and put your XP CD in and when it starts it will ask what you want to do, pick install XP...before it installs it will ask where you (which partition) want to install XP choose the drive # of the new formatted sony drive & let it do it's thing

After XP is installed remove the drives and change the jumper on old sony HD back to master, install boot up and install SP1 & updates, drivers and what ever.