Friend just dropped off his old computer.  It has a SATA drive running at the moment.  The motherboard has a connection for a PATA drive too.  He left the old PATA drive in the computer but it isn't attached to the motherboard.  He says that you can't have both hooked up at the same time. 

Before I start transfering files to a backup for him to put on his new computer is he correct?  I don't want to damage anything by hooking the PATA drive up now along with the SATA drive.  He says the PATA drive will boot the computer too so I can hook up each one individually.  It would just be less hassle if I could have all the drives hooked up at once and copy the contents over to a 1TB external drive. 

The computer is running Windows XP home.  It's a Dell 8400 with 512MB of ram.  I don't think any of that matters but just in case you wanted to know.

I had considered hooking up both and booting off a Linux CD.  I don't know which drive would end up as the boot drive if I hook both up.

I haven't been able to see to discover if they are set as Master, Slave or Cable Select.