Of course
Just format your drive (might need to fdisk if its partitioned), and pop your windows cd in, and it should be as good as new (note - you should make sure you *always* have a boot disk for this purpose)
Its also possible to dual boot linux and windows. From personal experience, the Mandrake install is very friendly and will automatically (if i remember correctly) add windows to the boot menu (lilo).
Another thing you could do that's a feature of Mandrake Linux is Linux for Windows, which basically runs Linux on your FAT32 (I don't know if NTFS is supported) drive. I've never tried this, but I've heard it works well for people interested in trying Linux out.
My final suggestion would be to use something like VMWare (
www.vmware.com) which allows you to run Linux within Windows, in a virtual pc environment. I've tried this before, and it works very well, especially since you can customize the hardware that's available to the virtual machine. Also, you can mount *.iso's (CD images) as virtual CD-Rom drives.