My two bobs worth.
It seems that to get the best from PI, you need a good 64 bit system with at least a 4Gb RAM and a 4 core processor. Then you can set it up to work really well. Windows 32 bit is limited in its RAM usage to 3.25Gb, so even if you stick another 2Gb of RAM in it, you will not get the full benefit of it.
I recently replaced the motherboard, RAM and processor in my machine and added a copy of Win 7 64 bit Home Premium. What a difference, everything works better!
