For those who need to know what to put in Poser to make it start below normal priority:

C:WindowsSystem32cmd.exe /c start "runbelownormal" /belownormal "H:Poser8Poser.exe"

Obviously your Poser install may be somewhere different.
See attached image where to put it. Basically put everything before my "H:Poser8....." in front of your P8 location in the properties screen.

Right click the icon, click properties. That gives you this window.
Afterward, when you doubleclick the icon, Poser will start up with the process already set to below normal, and you shouldn't have trouble using other programs while rendering.

Silke