Be careful on this one - I still have 5.5 as well as CS on my PC, and I pointed the plugins dir at my old 5.5 directory. All my third party plugins work fine, but it also tries to load the built in Adobe plugins as well, which have mostly been updated anyway, and some dont load. On top of that you end up with two blurs, two sharpens etc etc. I suggest any additional plugins you add within Photoshop you put within a separate folder (ie 3rd party or something) within the plugins directory so you can point at that.