ok, sounds like you're going to put in a new and larger IDE drive, and want to transfer the OS and contents of the 200GB drive to the new, then scrub the 200 to use as a data drive. Not a problem.
Give this thread a read, has a link to Drive Image XML (freeware) and how to change OS drives. Your's is slightly different, as it's two ide drives.
To RAID or not to RAID? (Not a WoW question...)
First up you get your new ide drive.
The jumper on your current 200GB drive should be on master and it should be at the end (black) plug of the ide cable.
Jumper the new drive to slave, connect to middle(grey) plug, hook up power, and boot up the computer. Your old OS drive, which it's running on, should show as c:, and the new drive won't show in my computer. Go to disk management - right click "my computer", select "manage", then "disk management" in the bottom left. This will open up and show the physical (incl. partitions) drives that are installed in your computer. Either the new partition wizard will auto-launch, or right click on the new drive and select "create new partition". Go through the wizard, then the new drive will show in my computer. Now you're ready to transfer data.
Install DI xml and do the drive to drive copy thing. Once it has completed, shut down the computer. It's quite easy to use, refer to the other post.
Now you change the cable and the jumper on the new drive to the master position. End of cable and jumper as specified by manufacturer. Unhook the old drive for now. Boot the machine, make sure everything is exactly as it was, just on a new hard drive. If all is good, shut down.
Hook up the old drive to the middle "slave" postion on the ide cable and set the jumper to slave, as well. Boot up and the old drive should show as just another hard drive, with the next available drive letter. You can assign any letter (almost) in disk management, if you so desire. If you want it as a data drive, go to disk management, right click and format it.