Am using Vista 64 bit OS and because I recently purchased Nik Software's Complete Ed was necessary to change from initial set up of PS CS4 64 bit to 32 for their usage compatability. Had Camera Raw 5.0 on 64 bit version, copied camera raw 8bi plug in file format and placed in correct file format folder for the 32 bit version of PS. ...sounds easy enough...but when I attempt to open a raw file in PS or bridge it will not open and get message - Could not complete your request because of a program error. Camera raw does show up and only once under the About Plug In submenu. Have tried Purge Cache option. Can still open raw files as always in 64 bit version, save and reopen 32bit version to continue but hoping for solution to eleminate that hassle. Thanks for your needed advice!
Plugin's have to be rewritten for a 64-bit environment so copying the 64-bit ACR to the 32-bit folder won't work. You need the 32-bit version of ACR in the 32-bit CS4 folder.
I'm not sure if the ACR 5.6 updater will work to update both versions, or if you need to download and install the plugin's manually.
You can get to the manual install ZIP by following the PSE link near the top of the regular ACR 5.6 page linked on the updates page: