Hi Ralph,
I skipped Vista as it wasn't an ideal OS for editing with - cant offer you any assistance in that area. You appear to have a need to update your graphics card to at least a 1gb to edit HD comfortably.
In my opinion you need to free up some space on your C drive. On your externals I suggest you get a "ping" software to keep them awake or you might get a PD whitescreen because the USB has slipped into sleep mode. I use NoSleepHDv2.0, I have it set to ping every 2 minutes.
The best thing is for you to test out PD10's trial and see how you get on.
Dafydd