<<1 PCI-Express 16x (free)
3 PCI-Express 1x (3 free)>>
<<"NVIDIA® GeForce™ 9100 GPU (VGA port)"
(I've got a slightly better AGP card, waiting. Can I use it in the "new" machine?)>>
It's onboard graphic and you can't put AGP card in it,it only takes PCI-Express graphic cards.
<<320 GB SATA 3G Hard Disk Drive (7200 rpm)"
(I need to put two other IDE HDDs in it - can I do this? >>
It should have IDE connection onboard(not 100% sure,no model number shown),and you can connect 2 IDE HDDs to if it does.