Do some research first. That question has been asked many times.
Short answer: Original XP had a maximum of 128GB support. Only with SP2 (or maybe SP1) that added extra support for over 128GB.
1) Create a main partition of 128GB and install on it. Install SP2. With software like partition magic, extend it.
2) Splitstream your CD with SP2. Google it!
3) Move to Vista!