The BIOS on this VIA motherboard only supports hard disks up to 137GB (when running in LBA mode). This has been confirmed by VIA's support channel whose comment (June 2011) in response to an enquiry about this was essentially:
"The maximum disk size is 137GB. The board is ancient and no longer supported. You should buy something new."
If you look at the metalwork at the top of unit you can see that there are a couple of carriers that can be used for adding additional hardware.
I have no idea what the one on the outside of the metal screen is for.
With that out of the way you can see one under the metalwork and just above the Power Supply
board. This is obviously designed to take a 2.5" disk drive. There is not a great deal of
clearance and any drive you fit has to be a slimline (9mm) one.
To get the carrier out you need to remove a screw at the top and a bolt on the back. The
carrier can then be removed.
It's a simple matter to screw a drive onto the frame using the four mounting holes.
To connect the drive in I chose to use the existing cable that was routed to the connector in the
foot of the 9450XE. To get at this you need to remove the metalwork at the top, undo the four
screws that hold the motherboard in place and remove pillars from the various sockets on the back panel.
You also need to unplug the riser card, remove the socket in the base and unplug the 44-pin cable
from it. With these out of the way it is possible to manipulate the motherboard to get it sufficiently
clear to let you get the cable out.
It would have been easier with the power supply board out of the way, but I found this difficult to remove and so left it in place.
This is with the cable clear and the motherboard refitted.
...and finally with all the metalwork back in place.
Power it up and you should find the disk drive has appeared in the BIOS.