Another thing is for PSPX is the update patches, do you have both the 10.02 and the 10.03 patch? The 10.02 broke the plug-ins from loading but 10.03 fixed that and some other stuff. You can find these on the corel web site and download them in order and allow them to install one at a time, without anything else running on your system.
This is all your plug-ins not showing now right? But they did in PSP9 at one time! If that is so then you do have them in the correct plug-in folder. Very few of the free plug-ins have a .exe file, mostly the paid one's do.
I think filter's Unlimited, Virzos, plug-in commander, Auto FX and such.
Let us know how this is going for you!!
Oh and you need an OPEN IMAGE for the plug-in command to be active, you can not see them if you just open PSP and try view the list!!