I've a 1 year old PC with:
Core2Duo 2.2Ghz,
Gigabyte motherboard 945GCM-S2C,
2GB DDR2 667Mhz RAM,
nVIDIA 8400gs 256MB Graphics card(Make- Xpert Vision).

The motherboard has:
2 PCI slots,
1 PCI Express x16 slot,
1PCI Express x1 slot.

Graphics card is in PCI-E x16 slot but nVIDIA control panel states that bus is PCI Express x8. No such slot exists on my Motherboard.
Why is this so? Kindly help.

slot-type is not the same as bus-type

slot is the thing that the card sits in
bus is sort of chip that controls data stream