if you're partitioning, leave about 5 gig. Once your c drive fills up your xp installation will be fecked. Also, the more ram you have the bigger the pagefile will be - from my own memory it defaults to 1.5 times the ram installed - eg 1 gig ram = 1.5 gig pagefile as well as the xp installation. you can change the pagefile settings if you know what you're doing though.