I read from the following page that adding a hard drive that used to be a WHS system drive to your storage pool can cause all kinds of problems unless you pre-format it first:
http://www.mediasmartserver.net/forums/viewtopic.php?f=5&t=12
Just curious if this is still true? My Acer WHS install CD comes with Power Pack 1.
I haven't tried it recently, but I wouldn't suggest trying it either.