dual boot install questions

Hi all,

I'm putting together a box for use at work. I want to try playing with linux yet again. I would like to dual boot with XP. For now I have a 20 gig HD.

1. Is 20 gig enough? I won't need a lot of file storage put will put Office (Word and Excell) on the XP install.

2. Is Knoppix (or maybe overclockix) a good choice or should I just go to a normal full distro like Debian or Gentoo since I'm installing to HD?

3. A rough outline of install procedure would be great i.e.- partition sizes, which OS first, etc./whatever

Thanks.