If your HD is partition with GPT style you can just resize down the partition from Disk Utility without losing data. Check the partition for errors beforehand just in case.
If the disc has MBR style you wont be able to do that easily, maybe latest versions of gparted or Parted Magic can do it but make a backup of your data before, HFS+ resizing can be dangerous.
There are also Mac-specific partition tools like iPartition or Drive Genius but they are designed for real macs so I'm not sure if they will perform well in hackintoshes and MBR.

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AsRock P45TS | C2D E8200 | GeForce 8600GTS
Mac OS X Snow Leopard 10.6.1 + Windows 7 Ultimate 6.1.7600 + Fedora 11