Attached Link: http://www.adobe.com/support/techdocs/330621.html

If you have WindowsXP with the SP2, that's the problem. SP2 blocks the HTML help files from being displayed, and is a know problem (see link). If you don't have XP/SP2 don't do a repair, but do a complete uninstall and then a fresh install (Note: pay attention to the uninstall options and you wont have to worry about reactivation). Photoshop (and all the CS2 programs) now use a separate program for Help called "Help Center" (you will find it in XX>Programs>Adobe>Adobe Help Center). I had a problem with my InDesignCS2 help, and found just doing a "repair" does nothing to the "Help Center", but a fresh re-install fixed it. SWAMP