I think that you can copy the original .exe instalation files if you have them on the drive, but copying something already installed will be difficult, you'd never track down all the relevant registry entries.
You could make an "image" of the drive or partition that the O.S. is installed on.This way you can preserve all your applications and updates and restore exactly as it was or choose which Files you back up.
To do this you will need a software programmes like Norton Ghost, Paragon Drive back Up and Acronis True Image (Cost more but more user friendly).
Also have a look at Bart-PE. There was an article about using this in a recent PCA.If you don't have a DVD burner you need software that will organise so you can back up onto several ISO format CD's
"Do i need to copy the whole drive ? I just need the OS and office 2000 from the machine?"
As it says above, you can't just copy off installed OS and/or programs. This is because changes are made on installation in folders you will not be aware of.
The best was to make a "safety copy" is to make an image of your olr system - this could then be re-copied onto another system - or with the rght program you can select items to restore - but not programs.
The nicest program to do this with is Acronis True Image, it's simple to use and an excellent investment for the future. Here is a link for a low cost version of TI click here - and a link for the free trial download click here (look for the download trial button)