NASLite is a much smaller and cleaner operating system than Windows XP so you don't need as much processor power or memory to run it. It also costs a lot less than a new WinXP CD. If you already have WinXP installed on the machine and are happy with the performance then it comes down to reliability. I have my NASLite box on 24/7 for weeks at a time without problems. Can't say the same for WinXP
NASLite only makes one partition on the drive. Each disk you install will appear as one network drive on a Windows PC.