transplanting my HDD
 

i have redhat 7 on a slave HD in one computer and i want to move it to another computer (still as a slave). can i do this? will configuration or anything get messed up? will it still dual boot?

You have LILO/GRUB probably on the first disk (in master disk MBR). In such case you'll need to reinstall it to the disk that will be master in the new machine. You'll also need to remove LILO/GRUB from the MBR it was in (using 'fdisk /mbr' from DOS/Windows boot disk).
The system configuration etc should be OK. You may only need to configure it to fit new hardware, but basic system should boot with no problem.