I don't think this is a conversion thing.
If I'm creating a bill, I can associate it with a Purchase Order. When I do this and the items have not been previously received, the items are received now.
This is a situation where we created a PO and sent it to a vendor, and the vendor sent us the items on the PO, but not the bill (yet). In order for us to facililate the invoicing of those items without getting into negative stock messiness, we need to receive the items into our inventory regardless of whether we have a bill or not.
So, we create the Item Receipt and associate it with a PO. This receives the items into our inventory without creating a bill.
Later on, we will receive a bill. So we have to create a bill and link it to a PO. That's fine, the basic functionality is there, but I can't see POs that have their items already received as an Item Receipt.
We don't want the items to be received again of course, until we create a bill the Accounts Payable gl won't get hit; Items receipts just receive the items, there's no AP impact.
This is along the same lines as what was discussed in this thread:
http://method.me/cs/forums/p/3268/12481.aspx#12481
Logically, if we send out a PO to a supplier, there must be a bill at some point later on that we can tie to that PO, regardless of whether that PO's items get received; somebody has to pay for them at some time.