If it's a new drive (ie. no data), then it won't be a problem. If you're going to dual boot with something like windows, I would suggest partitioning the drive in half, then installing windows first (as it has a tendency to overwrite any bootloader and make other os's unreachable) then install your rh, which will happily coexist with windows. RH should paritition things for you (you just assign it the freespace on your drive that it's to use) or you can manually partition... your choice. From there, it will install GRUB (bootloader) by default or you can choose to install LILO (LInuxLOader) onto your MBR which will then give you the option at boottime as to which OS you care to load. And that's roughly that.
If you have data on the drive already, like an OS or whatever, and you don't want to wipe it, then you'd have to use something like parition magic or whatever other progs are out there to sesize your partition so that you have unassigned freespace on your drive for linux to sit on.
