Ive never seen a dual motherboard like that.
go here for some socket 423 boards
http://store.yahoo.com/justdeals/motherboards2.html
They do charge like $12.95 shipping for the first item and $3 or $4 for other items
Make sure when you look at the motherboards that you notice the memory types.
Most of the ones you can find now use PC133 or Rambus.
Both of those options sort of suck.
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You could get a socket 478 celeron....otherwise I think id rather invest my money in a P4 for the 478 board than to go backwards and spend money on a weak socket 423 setup.
JP