the preference file (Prefs.psp) is located in the Documents and Settings/[user profile]/Application Data/Adobe/Photoshop/[version]/Adobe Photoshop [version] Settings folder...

whenever things start acting screw-bally on me i like to force Photoshop to create a new preference file by holding down the Shift-Ctrl-Alt when i launch.

a lot of time whenever PS gets all WONKY, tossing the "prefs" file fixes it up (and it's a lot less painful than "re-installing" PS)

hope it helps
retrocity