The GB question that is asked by Boot Camp when partitioning is not only about the web site, so one has to make adequate provision for the operating system and any additional software that may be installed. The advisable allocation for Windows 7 is 50GB but the minimum is far less. Say that only CSB is run. CSB only requires less than 50 MB to function. If your tlx file and web site goodies is say 500MB of disk space, you would need 50GB+50MB+500MB=50.55GB. However, as software is added as time goes by, anything under 150GB will probably cause a major headache so its better to be prepared now than sorry later.
I don't think Windows XP is available any more, but if it were it would be a huge download eating up a lot of bandwidth.