dual boot -WINNT and LINUX

I am Hoay fern and wish to ask about dual boot.

Currently we have LINUX operating system installed in Compaq Prosignia 300 with tape drive, so we wish to use it as WINNT backup.

So we need to install WINNT in Compaq Prosignia 300 with existing LINUX operating System.
May I ask :
1)How can I found what whether we have enough hardisk space or not ? I mean what are the commands.

2)How can we create dual boot with existing LINUX Operating System?

Please assists

hoay fern (hoayfern.lee@duraco.com.sg)