I forgot to mention: I have already partitioned (via PartitionMagic) my HDD into 2 partitions C: and D:.
I want to clone Win XP Pro currently on C: and image it on D: and avoid the arduous process of
installing the same OS on D: again.
It'd take a little more than just cloning.
You'd have to adjust all the registry data on the D drive installation to tell that windows that it resides on another drive.
You'd also have to add an operating system to the boot loader to inform your system there's something on the D drive now. That actually isn't as hard as it sounds -- Click Start, right-click on My Computer, and go into Properties. In the Advanced tab, in the Startup and Recovery section, at the top you'll see some options about which OS to boot, how long to display the options, etc. One of them should be something like "Manually edit file" (I cannot say what exactly, as I'm using Vista.) In there you'll probably only have one OS listed -- the one on the C-Drive. Edit that file so that it points to the OS on both the C and D drive. There's a couple other options to fiddle with there, and if you did it right hopefully next time you reboot you'll get a menu for which OS to boot into. But, it's not to say it'll be that simple.
Also, whenever messing with the boot loader of any OS it's a good idea to make sure you have access to the Recovery Console, either by installing it onto the machine or having the XP Install disk hand.
Still, probably the best way to do this would be to simply reinstall it. If you hate sitting there (as we all do) going through the options, consider making a SIF file. A sif file is simply a file that has the answers to all of the questions that Windows asks during setup -- where to install, product key, time zone, etc., etc. To do this you'll need a floppy drive, as XP's setup looks for it to find the sif file.
http://www.networkclue.com/os/Windows/install/unattended-install.aspx has some good help for creating one of these.
