According to my experience, Knoppix 3.7 installed on a hard drive is over 2GB (about 2.2GB) for the root partition. Since you have 64MB of RAM you will also need a swap partition. This is why I said you might be able to do it with a 2GB HD, but it is most likely impossible. This is why I suggested you get Debian because Knoppix installed on a hard drive really Debian unstable.

Perhaps someone else can confirm the requirements.

I hope this helps.
James