I want to install debian on a previously used computer from scratch. Can you give me some tips about how can I achieve this. The following is a description of hardware:

Pentium1 200MHz MMX CPU
Hard drive 6G
Realtek Network card
Conexant chipset modem

Be sure you know what you have for hardware and follow the prompts. The only thing that confuses people about Debian is the detail to which the installer asks you what you have for hardware. Its the first distro I successfully installed (on a p-133, at that).

BTW, if you're planning a graphical environment, I'd suggest you try something other than KDE or Gnome. They're both a bit top-heavy for that machine. They'd run, but not very fast. I have changed my mind about XFCE. I'd recommend XFCE4 as a choice for Graphical environment over any others, as it seems to be quite easy to configure (although Windowmaker and Debian seem to blend soooo well.)

Where can I find XFCE4 for download and how can i Install it in debian

It should be a choice on your cdrom (perhaps cd2) If not, apt-get install xfce4

Go to the Debian website and click on the packages section. You can see what's available for stable, testing, and unstable. Check them out (its the biggest repository of any distro, so it chock full). You might want to read the installation notes carefully before you install. It'll save you a lot of questions. Not bad for an hour's reading.

IIRC, it's in Sid.

I have a system, which is very similar to yours which is currently running Debian and Gnome .

I just wanted to backup what vectordrake stated. They system runs ok, however it is working very hard to run the current testing install of gnome and having several things open at the same time will seriously effect system performance to the point I would not reccemond using it.

Hope this helps.