I'll go on and say this then...
Macs (new ones) have PCI-X (which as everyone has stated is not PCI express). I saw PCI-X on Xeon boards well before Apple shipped a box w/it.
Windows keeps dll's in memory after use for 'a while'.
You can prevent this to help quickly free memory for swap and other apps by changing a registry setting:
There are other tweaks too, like not paging out any kernel code or keeping multiple copies of dll's for stabilty. Gotta have 1GB for most of them to be helpful though.
I'll go on and say this then... Macs (new ones) have PCI-X (which as everyone has stated is not PCI express). I saw PCI-X on Xeon boards well before Apple shipped a box w/it.