The 250GB half mac and half bootcamp with windows xp were almost full and I like to have most of my documents, photos, videos in the internal drive. I have also some external hard drive but all ntfs (windows).
I decided to buy a 750GB to have half Mac and Half windows. No problem with superduper! As described in ifixit video but it took me more then 2 weeks to understand how to clone the bootcamp partition. After some Internet research I understood I need a partition in one of my external drive but did not understand if fat32, ntfs or apple format (and later I discovered needs Apple format) so I created 3 different partition 1 ntfs and 2 fat32 with a program name magic partition then with Mac os I have changed 1 fat32 in apple format. After that with Winclone 2.2 I tried to clone the internal bootcamp partition in the esternal hard drive apple format but no way, always an error at the beginnig of the process. Then looking in Internet I find the right suggestion: configuring winclone check just 2 voices (no compression) and at the moment i remember just 1: windows xp so I create the image and than i follow the instruction how to clone the bootcamp partition and everything now is ok.
You need an external hard drive with an Apple format partition with more then the space of Bootcamp (because in compression in my case winclone give an error) and be carefull with the configuration, chek just the minimum.