NAS device
The HP Microservers offer a flexible approach to a DIY NAS solution. The hardware has
* dual core AMD processor * DIMM slots to allow upto 8G RAM * 1 GByte ethernet * 4 * 3.5" SATA drive bays * 1 * 5.25" drive bay intended for optical drive.
There are 2 models (that I know of) of the microserver - the older N36L and the more recent (as of Feb 2012) N40L.
The servers have a very attractive price of £220 and there have been regular offers where there is a £100 cashback - so the price comes in at £220 * 1.2 (to include VAT) - £100 so about £142. UPgrading memory to 2*4G DIMMs with third party and the price is still less than £200.
For a NAS device there is little requirement for an optical drive so it would seem reasonable to put a 5th hard disk into the top bay - one of these looks attractive to mount a 3.5" disk in the 5.25" bay : http://www.amazon.co.uk/gp/product/B000KS8S9W/ref=oh_o01_s01_i00_details
However, the BIOS as delivered is configured to not allow the 5th SATA port to run at 3.0G and there are reports of performance issues when mixing