Problems moving files from XP HD to Vista HD

I am trying to put a ATA hard drive into a SATA system to move the files over (and I will keep it hooked up if it all works). The ATA hard drive has XP on it and the new computer uses Vista. Vista will boot, but in "My Computer" it says the second hard drive must be formated before it can be used. any way around this?

Thanks.

 

Does the XP Hard disk still work in the PC it came from?

 

The PC it came from is dead. But it did boot in the new PC. I am going to just boot it from the XP drive, and move the files over from there I guess.

 

That may or may not work, depending on how different the two systems are.

 

Update: I changed the old HD's jumper setting from Slave to Master. It now boots from the new (Vista) HD, and recognizes the old one.