I want to install Debian Linux O/S on my computer.?

If you are new to Linux I would suggest installing Ubuntu 9.10 within Windows

Installing Ubuntu as a dual-boot with Windows without partitioning

http://www.psychocats.net/ubuntu/wubi

You keep Windows as it is, Wubi only adds an extra option to boot into Ubuntu. Wubi does not require you to modify the partitions of your PC, or to use a different bootloader, and does not install special drivers. It works just like any other application.

Wubi keeps most of the files in one folder, and if you do not like it, you can simply uninstall it as any other application.

Boot in to windows insert the Ubuntu 9.10 LiveCD and you will offered the option of installing inside windows which is where the Wubi installer comes in, you will be asked how many gigabytes you wish to allocate to Ubuntu (I recommend 8gb) then you set a password for your installation then click install and thats it.

Once Ubuntu is fully installed upon starting your PC you will be given a choice of which operating system you want to use Windows or Ubuntu

Ubuntu 9.10 Download

http://www.ubuntu.com/getubuntu/download

Ubuntu 9.10 (Karmic Koala) User Guide

http://ubuntuguide.org/wiki/Ubuntu:Karmic

LUg.

Debian Linux is one of the finest operating systems that you can find today. Don't listen to all those who are telling you that Ubuntu is better, because you will find that the number of opinions is as large as the number of Linux users :)

First of all, prepare for the installation (backup important data just in case) and plan which partition you are going to dedicate to Linux. If you currently have Windows installed on C: and there is a drive D: on another partition of the system, then you should clear up all the data on that partition and use it in the Linux installation. If you don't have a partition you can spare, you will need to reinstall Windows first - and this time make it a smaller partition.

Note also that you will be making 2 partitions on the empty space for Linux: one small partition (about 2GB) for swap and the rest of the space for the / (the "root") partition.

It would be better to repartition. Most install processes give you this opportunity.

Since you asked the question, I can make some assumptions about your experience. I recommend you try the latest ubuntu, which is a repackaging of debian with very good install and config defaults and controls.