QUOTE (Zertz @ Nov 2 2009, 07:20 PM)

From what I'm seeing
here, it looks like a BTX motherboard, but it could still be some proprietary "standard" as well. Kind of hard to tell. However, from what I could find, I don't think the Antec 300 has holes for BTX boards anyway.
The other components look standard, no funky heatsink or power supply.
I don't think that's BTX, the motherboard would be 'upside down' and the case would open from the other side.
http://www.anandtech.com/showdoc.aspx?i=1876&p=2With the heatsinks and fans from the pictures, it looks to be pretty straight forward.
The power supply shouldn't be an issue if you're swapping that out (just make sure it has all the proper connectors - it's quick to verify if you just pop open the case and look at where the wires go on the motherboard). There should be a 24-pin and a 4-pin or 8-pin CPU connector. Possibly some other auxiliary power connectors. With that said, I doubt a modern power supply will lack the connectors unless Dell is using some funky proprietary stuff

You might have a little trouble with the I/O bracket on the back of the motherboard. I'm not sure if the shape is standard.