With windows 7.
If you have an external HDD. I would:
(1) Back up all of your files to the Backup USB HDD. Verify backup then delete from HDD.
(2) Disable Hibernation file and reboot.
(3) Using Win 7 Diskmanager, shring volume to the Size that you want for your Operating system Plus Programs (ie 60 -> 100 Gigs).
(4) Now create additional partitions, or or Format, in the remainder of the HDD
As a safty measure:
(1) Using win 7 back up. (1) Image your "C-Drive" to the Backup HDD.(2) Select make recovery disk - This will create a bootable DVD that will alow you to restor this Image file to a New HDD, or to your original Hard drive should it fail. Added - You can make this back-up to DVDs, usually takes from 3 ->5 DVDs not counting the recovery Disk.
Hibernation file
To make hibernation unavailable, follow these steps:
Click Start, and then type cmd in the Start Search box.
In the search results list, right-click Command Prompt, and then click Run as Administrator.
When you are prompted by User Account Control, click Continue.
At the command prompt, type powercfg.exe /hibernate off, and then press ENTER.
Type exit and then press ENTER to close the Command Prompt window.
Play it safe and also disable sleep mode in control panel Power setting panel. Don't for get to reboot.
Reason you have to disable Hibernation is to get rid of a hidden file that windows sticks at the end of the Disk. Prevents shrinking volume.
To re-enable change OFF to On.