32 bit XP does not support drives larger than 2T. There is a format tool for external drives that make the larger drives work on XP. I don’t know if they have something similar for the internal drives. See if this helps http://hothardware.com/Articles/WDs-1TB-Caviar-Green-w-Advanced-Format-Windows-XP-Users-Pay-Attention/ or this on advanced format tab http://www.wdc.com/en/products/products.aspx?id=120
Joe
