Latitude E6400

Latitude laptops from this era feature an underpowered Core2 Duo processor in the Penryn-3M family and DDR2 RAM that only runs at 800MHz. All RAM modules have what's called "system timings". The Dell-supplied RAM for the E6400 only had timings of 4-4-4-12. The combination of weak CPU and slow RAM will not all the E6400 to run Windows 10 effectively. Laptops from this era came with Vista preinstalled. It is true that installation keys for Windows 7 will allow the installation of Windows 10. However, Vista keys will not allow installations of Windows 7. Some refurbishers are not "blessed" by Micro$soft. Instead of buying a (very expensive) multi-install key from Microsoft, refurbishers will find workarounds to get the OS installed. This is what leads to may of the problems that are discussed in other reviews. Unless you know exactly how to install a solid-state hard drive and know how to install a lightweight Linux-based operating system such as Lubuntu or Puppy Linux, "Average Joe" or "Average Jane" should stay away. Spend the extra money... Purchase a new machine that will run both the current Windows 10 and the future Windows 11.