BX80557430 Intel® Celeron® 430 -1.80GHZ 512K Cache, 800Mhz Frontside Bus, Intel EM64T, Execute Disable Bit 284.00
G31M-S ASROCK G31M-S - CHIPSET : Intel G31 + ICH7 ,1600/1333/1066/800 MHz (FSB), Socket T (LGA775) 279.00
CPU COMPATIBILITY : Intel®Core™2 Extreme, Intel®Core™2 Quad, Core™2 Duo,Pentium® Dual-Core, Pentium® D, Pentium® 4, Celeron® D,Celeron® processors
MEM COMPATIBILITY : Dual channel DDR2 800/667 x 2 DIMMS Max 8 Gb
HDD COMPATIBILTIY : ATA x 1, SATA II x 4
ONBOARD : 1 x PCIe x16, 1 x PCIe x1, 2 x PCI, 5.1 channel Audio, 10/100 LAN, 4 USB 2.0 ports
128X64DDR2800 1024MB, 800Mhz, DDR2, 240-Pin Memory Module - HYNIX 189.00
HD502HJ SAMSUNG SATA2 500GB 7200RPM 16MB HDD 395.00
These are the cheapest components I could find on a local supplier pricelist. Add vat.
As your question did not have any criteria like quality, or quantity. You can build pretty much anything your budget allows.
By doing some more browsing, I'm sure you will be able to find a product cheaper here or there...
As for quality, I personally have never used Samsung hard drives (the most important part of a file server)... personally I'm a die-hard Seagate fan, but I've heard people applaud and shun Samsung... pretty much 50/50 there... ram... pretty much any would do... given its from a reputable supplier, and comes with at least 1 year warranty, again brand names, like Kingston/Kingmax, etc can signify better quality, but that's debatable. (And for those who say they can't survive without OCZ ram, they obviously arent working for a living, or live off a trust fund i.e Mommy and Daddy)
The CPU is Intel... uhm... maybe you will find a knockoff in Lesotho... dunno.
and of coarse... the Mobo... again... quality wasnt specified.... Asrock/Foxconn/MSI,etc are the bottom of the pile, with Intel, Gigabyte and Asus at the top.. so from say R300 to R10000 for Desktop/Workstation boards... I have a 'lil foxconn mobo in a home fileserver, that's been running for over two years now, and not a day's problems... I also have a full-on blade (Xeon, 8GB ram, 6TB SAS doing the same job at work)... so it goes to show what job (load) will the computer be doing...
anyone else like to add something?