On a 64 bits Windows machine, the photoshop setup installs the 64 bits and the 32 bits versions as independant programs. Many plugins won't install in the 64 bits photoshop version, so that's why the 32 bits version is important even on a 64 bits machine...
Now for this problem with bridge, here is how to do:
-Open Bridge and go to Edit/Preferences/File type Associations and go to the item jpeg and click on the small arrow and then click browse. Then go to your C drive and open the program (x86) folder and pick the photoshop.exe file, click open and then OK.
Now, when you will select a jpeg picture in Bridge, you will have a new photoshop (default) option and this will open the jpeg in Photoshop CS5 32 bits (instead of 64 bits).
You can do the same operations with other image files extensions such as tiff if you need this.