I took too long posting so the pics came up before my post. :b That is most definitely a PCI only motherboard. Stock powersupply is only 250 watts. Max memory is 2GB. Memory type is DDR.
As far as upgrading to a newer system, to do it in stages you'd need a motherboard with an LGA775 socket to use the old processor. (2004/2005 is probably when I built my first system, replacing my aging Compaq. PCI-Express and DDR2 were new back then.)
To get a system with decent upgradability, you'd need to replace the motherboard, memory, (DDR motherboards are almost extinct) possibly power supply, and would probably need an IDE/PATA card. (I counted at least 3 drives, 2 optical and at least 1 harddrive. Most modern motherboards only support 2 IDE/PATA devices and instead have a bunch of SATA ports.)
So a full upgrade would probably cost more then $100.