To resize or combine partitions without destroying existing data requires additional partitioning software, but even then a backup of existing data is recommended before running such software. Windows does not have any built-in utility for re-organising partitions without destroying existing data.
Most well-known commercial software for re-partitioning without data loss is Partition Magic:
http://www.symantec.com/norton/partitionmagic
Alternative:
Partition Manager Express (FREE):
http://www.paragon-software.com/home/pm-express/