The beauty of a Mandrake installation is that you can leave Windows untouched during your install process.
Don't have more than one partition on your HD? No biggie. :) Mandrake will ask you how much of your drive you want to leave for Windows, "non-destructively" split the drive into the appropriate paritions and set up the boot loader with a dual boot between Windows and Linux. Priceless and painless. :)
Mandrake's installation process is a beautiful thing. 8)
You might want to let it go the dual boot route the first time around just in the unlikely event that Mandrake has trouble with a piece of hardware in your system.
Just don't do the automatic software update at the end of the installation process. hehe After you're installed go to the Mandrake Control Center > Software > Software Sources and make sure it has a valid address in the remote software source. Once that is set then you can do the software update.
Another thing; during the mouse config step of the installation if the mouse starts acting squirrelly just give it a moment to settle down. It will pass, the mouse will work and you can proceed with the installation. :)
But, hopefully those will be corrected by the time the boxed set ships. They are extremely minor but for a new user could present a bit of concern. Especially the software update as when it happened to me my system hung for a long time while looking for a bogus update site. I finally just hit the reset button. hehe