Any Linux live-cd will resize your partition using Gparted (usually in 'system tools'). Just defrag your Windows system and back-up any valuable files (although if it's the first partition it's easier as it will use free space to enlarge the partition or maybe you should care with the files in the next partition..you'll see).
Try SliTaz http://www.slitaz.org/en/ , it's only 30MB and you'll have a lightning fast linux o.s. to play around.