While I’ve never used that command, I noticed while mapping the menu items for Photobars that it disappeared in going from PS7 to PSCS. As I recall, I believe someone told me it was replaced with the reportedly more correct name of "Create Clipping Mask" in the Layer menu. You might try that and see if it gives you what you’re after.
Regards,
Daryl
In Ps 6, 7, Cs, the shortcut was CTRL+G, now in CS2,it is CTRL+ALT+G Or ALT+click between the two layers in the layers palette.
The menu entry is still Layer>Create Clipping Mask
But keep in mind that the keyboard shortcut can be anything you want it to be.
Bob