Hmm. Only one DIMM slot, so that won't work... It's a hardware problem, and not easy to diagnose. May well be the Motherboard. The only other easily replaceable part is the HDD, commonly available on Ebay (2.5" SATA), might be worth a try.
And a Motherboard available for £63 if you have a teccy Dad/Brother/pal to fit it.http://www.ebay.co.uk/itm/Acer-Aspire-One-NAV50-LA-5651P-Motherboard-/290753233798?pt=UK_Computing_CPUs_Processors&hash=item43b23e4386