if your disk is partitioned in the GUID partition scheme already, you can... if MBR, nope. You'd have to make an image of your install and place it somewhere else, then do a restore using the install DVD and reinstalling chameleon.

if you have GUID, simply use Disk Utility and resize your partition and create a second behind it. All should work as normal.

EDIT: with MBR, it is possible, just problematic at times... Thanks Dies.

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