Monitor your resources when you test. How long does the HD use to fire up P8 until it stops. How much does the Poser.exe allocate in the ram, how much does it cache.
And do it just after a reboot - if you already had it loaded before does not count. Then everything will be loaded from the ram and not HD.
Windows tells me that 450MB ram is allocated to Poser.exe. But since 2GB have been cached - why does it do that when PoserPro doesn't?
I have 120GB of content in 9000 folders and about 300.000 files and my P8 content hasn't even been installed yet :-)