I have a Windows XP key so I can legally use Windows XP. I want to install Windows XP SP3 on my 64GB MBA running the latest OSX with Bootcamp. I only need Windows XP SP3 so I can use Ninja Trader. So, I do not need much space. I do not have an optical drive, I cannot borrow one etc. Questions: 1) Where can I get Windows XP SP3. 2) How much space will I need for Windows XP SP3, and some programs (such as Ninja Trader). Is 10GB ok? 3) How do I use Bootcamp to install Windows XP SP3 and get it working correctly? When I tried to install Windows 7 Ultimate I had a problem where the partition wasn't formatted to NFTS (or something like that) even though Bootcamp created the partition in the first place! Basically I need to install Windows XP SP3 from a USB and I have a key so I can use a real version.