you may be able to use more memory
post system specs of the 2 machines
leave the original xp alone if it's booting without errors
add the other one to the 2nd ide channel as slave check your optical drive
you may want to set the 2nd HDD to cable select if the optical drive is set for this
or you cam set the optical to master and set 2nd HDD to slave
some systems like CS better make sure if using CS that the 2nd drive is in the middle of cable
I like to keep the optical as master on 2nd IDE
thats just me
after you have this setup
boot to your machine
don't worry if you can't see the drive
go to my computer right click this icon go to manage nav down to disk management drive should be there you will need to take possession or ownership of the drive to use it
right click on drive go to properties advanced