I agree with Adrian. Sunny you've got a very daring way of installing Linux.
Install Windows (my windows partition uses 10GB of an 80GB drive) in a partition, not on the whole drive.
Install Linux in the free space (remembering to leave room for swap).
Use LILO/GRUB as the boot manager. Don't tell people what you're using, some linux fatties are quite the GNU zealots, while others don't give a rats. You get a zealot going and they're hard to stop.
http://www.linuxquestions.org/questions/showthread.php?s=&threadid=224547 <--- There's a nice place to go if you're having trouble with Debian post install (It's really useful). If Linux is going to be accessing the Internet, then ensure you have iptables set up. Guarddog is a nice config program for iptables, and it's graphical.
Also, if you want to share common space, you could install a FAT32 partition, as both Linux and Windows accesses FAT32. You COULD use NTFS (since write support is enabled, but it's not the most stable, and from kernel to kernel YMMV), though I suggest FAT32. Maybe a later kernel will have nicer access.
No offence to sunny, but don't listen to how he installs Linux. It's more work than necessary. Since you're installing Debian (great choice by the way, in my opinion one of the better distros), follow the three steps that Adrian put in (of course the free space needs a small logical partition for swap). Go to
http://www.debian.org and read the install guide before you make any decisions. Debian isn't a hard distro (forget what elitist fatties say, it's not hard), but you do need to know about your comptuer. Read the guide (well, skim it), and read a Linux guide.
You might decide that Linux is a piece of crap and it's easier to do uni work on Cygwin. Or you might decide that you Like linux and end up using it for everything, like I do.