Most HP's use up all four Primary partitions for Recovery, Tools, System Reserved and OS.
If this is the case the best path forward is to boot free Partition Wizard bootable CD
to convert C to Logical, then Resize it as desired to create an adjacent Logical data partition.
Be sure to make your Recovery Disks first: HP Recover Windows 7 Operating System Using HP Recovery - HP Customer Care (United States - English)
Since HP has the worst load of bloatware and useless factory utilties in the industry, you may also wish to Clean Up Factory Bloatware