Yes, you CAN replace the board. The problem is, it's a Dell board. It's probably ATX sized and in an ATX case, but with a Dell proprietary power supply and Intel OEM style front panel connector.
You already know it's easy enough to put a standard power supply in. But then you have a couple other problems: The backplate is steel, you'd have to remove it for any board that didn't have the exact same port configuration. And the front panel connector would have to be re-wired with standard leads for most boards to fit.
I've actually done this. I occasionally remove the wire leads from old cases, I've removed the front panel switchboard, the cable clip that holds the ribbon cable in place, and replaced the ribbon cable with wire leads. It's not that difficult, because you can actually see where all the traces go on that card. Follow the power button traces to the cable connector and install the wires for the power button, etc.
As for the back panel, you can go shieldless, or you can remove the outer cover from the inner shield to expose a full set of port holes on the inner shield. Then it's simply a matter of finding a board with traditional port locations, now that you have all of the traditional port holes open.
If you remove the panel completely, you can install other boards with non-standard ports. But the hole that's filled with that cover is shorter than a standard backplate, and I've found that board with 3-high audio connectors (as opposed to the standard 3-wide configuration) will have the top audio port half covered with the sheet metal. I suppose you could notch the case for it, but it would be far easier to simply select a board with the old standard port locations.
Gateway also used the Intel OEM style front panel connector that Dell used. Gateway also used standard power. So a Gateway motherboard would allow you to change to standard power without modifying the front panel connector. Unfortunately the only Gateway board I have for you is Slot-1 and only supports 66/100MHz bus speeds. Your PIII 667 uses a 133MHz bus and would show up on this board as a PIII 500.
The old Dell plastic case used on P-MMX, PII, and PIII processors is actually a very nice Palo Alto case. Palo Alto unfortunately didn't make room for a standard-sized replacable port cover.
Would you like to upgrade your board for a different processor? I could held you find a board with standard port locations that wouldn't interfere with the case.
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