What is PAE, NX, and SSE2 and why does my PC need to support them to run Windows 8?
Physical Address Extension (PAE), NX processor bit (NX), and Streaming SIMD Extensions 2 (SSE2) refer to features of the processor. PAE enables 32-bit processors to access more than 4 GB of physical memory on capable versions of Windows and is a prerequisite for NX. NX allows the processor to help guard the PC from attacks by malicious software. SSE2 (a standard on processors for a long time) is an instruction set that is increasingly used by third-party apps and drivers. For Windows 8, for your malware defense features to work reliably we require that your processor support NX. To enhance the reliability of third-party apps and drivers running in Windows 8, SSE2 is also required. If your PC doesn't support PAE, NX, and SSE2 you won’t be able to install Windows 8. Upgrade Assistant will provide you with an error message if your processor doesn't support PAE and SSE2. You'll also see a notice if the processor might not support NX or if NX is turned off in the PC BIOS. Windows 8 Setup will attempt to turn on NX during installation and, if it isn't able to, will return your PC to the current operating system.
You can check if your processor supports NX and can turn it on if it is turned off by going into your PC's BIOS. Accessing the BIOS can vary depending on your PC manufacturer. Usually, you must press a key (such as F2, F12, Delete, or Esc) or a key combination immediately after you turn on your PC before Windows starts. For more information, check the information that came with your PC or go to the PC manufacturer's website. Once you're in the BIOS, look for the NX or XD settings under the Security tab to turn on the NX support. If the BIOS setting for the NX support option isn't available on your PC, you might need to contact the PC manufacturer for info on updating the BIOS. If you need help accessing the BIOS on your PC or turning on NX, you can contact support.
If you do purchase Windows 8 and can't install it, contact support for assistance.