Which Windows version, and with what did he try to resize it? Has he messed up his Windows installation, or does it still work?
A pretty nice working combination is a Linux live CD like Kanotix which has qtparted. qtparted can resize NTFS and other partitions. After that, you should use Linux cfdisk or fdisk to manage the partition table. Stay away from winbloze-based "tools" unless you like reinstalling stuff