i finally found the free software to resize i mean enlarze my C drive partition without reinstalling the os. This Free Partition Manager--EASEUS Partition Master Home Edition is a partition magic alternative and partition management freeware. With its help, you can resize/move, copy, create, delete, format, hide, explore hard disk drive partitions. To extend system partition, have better disk space management, settle low disk space problem! The most attractive feature is it can resize/move partition without destroying data. This free partition manager is an ALL-IN-ONE partition solution and disk management utility. It allows you to extend partition (especially for system drive), manage disk space easily, settle low disk space problem under Windows 2000/XP/Vista/Windows 7 (Only for 32 bit). The most popular hard disk management functions are brought together with powerful data protection including: Partition Manager, Partition Recovery Wizard and Disk & Partition Copy Wizard.

you can get it from here and i think we should thank them to provide this as a free software.

http://www.partition-tool.com/personal.htm