Boot Grub Menu.lst

What if you installed and got XP running on the 20gb partition, then went back and installed linux after xp was up and running. I am not an expert with Grub but this is how I have done it in the past. Partition all your drives first to how you prefer, install xp on the preferred partition then linux on the preferred, during the linux setup grub should detect the different drives and automatically add entries for XP and linux. source

You sound like someone who wants to change out frequently for testing. I would recommend VMing distros to get started until you get comfortable and find the version you like the best. source

If the md5 sum is bad then there's no point in further trying to define a problem. You could indeed have multiple problems, but the md5 has to be correct before you can expect to go further. My best recomendation is still to restart the torrent with the files all still in place, BityTorrent will check the files and repair any damage. source