Sorry, its my mistake not to ask you first for what reason you want to make partitions.
It is not necessary for the reason Windows 7 works with NTFS formatted harddisk. Better management today then with the earlier FAT16 and FAT32.
But perhaps you want to split into one partition with Windows 7 and one with only data to minimalize the risk of data loss with when Windows might crash one day and your backup is by accident not up to date (Murphys law, you know

).
How to make partitions is difficult for me to explain in English (easier to do then to tell), but perhaps you can do with this link:
http://www.sevenforums.com/tutorials/2674-partition-volume-create-new.htmlBefore trying again read this first:
(This is when you dont have an installation CD, but only a hidden partition on the harddisk with Windows recovery software on it.)
It is possible that you are not allowed to narrow the partition with Windows 7 installed. This is for the reason of a hidden partition on the harddisk with recovery software instead of an installation CD/DVD.
The recovery software doesnt work anymore after resizing the partition, so then you are not able anymore to bring your computer back to the factory settings and you lost your Windows 7 license.
After a crash you have to remove the new partition first otherwise you cant recover the system.