Converting 320MB HTML to MOBI

Hi everyone,

I have used HTTrack to download the entire Stanford Encyclopaedia of Philosophy. http://plato.stanford.edu/contents.html

It's produced a big HTML folder of 320MB. I opened it with calibre, and it showed its size as 112MB; then I tried to convert it to MOBI, and it ran all night, stuck on 47%.

Is this project simply not feasible, or is there a way of making calibre capable of doing it?

Thank you very much for your help,
noctilux