you may just have PATA controllers with it. click here
Unless you have SATA compatability on the motherboard, look at some 7200, 16Mb cache hard drives. They might not spin as fast as the 10k's you have, but you will get a lot of storage per Gb and they will not be to far behind.
You could then *clone * over the OS and data from the main 36Gb SCSI to the PATA hard drive. £58 for a
If you do have SATA ports, check to see if theyb are SATA11 compatable. These are the fastest.