Og Lifebook should be increased from 4 to 8 GB, to prevent frequent crashes. The memory usage under certain conditions of use was with 4 GB DDR3 RAM to the 95%. So upgrade to 8 GB ... Fujitsu PC or laptops are in our experience something picky respect. RAM placement, so I asked to work on the dealer I trust. I found after a brief correspondence and consultation with Mr. Mihatsch (Mihatsch Trading) who is extremely knowledgeable and very quickly (I have repeatedly bought in this company), the right, the same type of module. The shipment was carried out 2 hours after ordering, the "normal" delivery could be obtained 20 hours after the order in the house and thus just as fast as with PRIME shipping. The module has achieved since the same type to the already installed and Fujitsu certified module expected his job and above crashes a thing of the past. Both module and distributors 5 star and absolute recommendation for the great service!