NX Is also called execute disable bit. Go into BIOS and select CPU feature from the frequency/voltage control menu. Make sure execute disable bit is enabled.
Windows 8 supports secure boot. Windows 8 will still run on legacy computers that do not support secure boot so you should be okay.
From the Microsoft Web Page
What does Upgrade Assistant do?
There are four main things that Upgrade Assistant does:
It scans your hardware, apps, and connected devices to see if they'll work with Windows 8.
Make sure all the peripheral devices that you need to work with your
PC, like printers and monitors, are connected to your PC and turned on
before you run Upgrade Assistant.
Upgrade Assistant checks your PC hardware to see if it meets the Windows 8 system requirements
to install on your PC, including features of the processor such as CPU speed, PAE, NX, and SSE2, as well as RAM size and hard disk capacity. It also checks for compatibility of your currently installed apps and devices.
It provides a compatibility report. Windows 8 generally works with the same apps and devices that work with Windows 7,
but in some cases, a product might need an update, or you might need to
uninstall and reinstall it after you upgrade. The compatibility report
lists your apps and devices that will work in Windows 8,
those that might not work, and what you can do to get them working
again after you upgrade. If some of your apps and devices aren’t listed,
it might be because we don't have compatibility info for that product
yet. For more info on specific products, check the Windows Compatibility Center
, or contact the product manufacturer.
You can save or print the compatibility report to use
later. Unless you choose the option to "keep nothing" during the
upgrade, you'll be able to find the report on your desktop after the
upgrade. For more info, see
Get your apps and devices working in Windows 8.
It checks your PC for support of certain Windows 8 features
. Specifically: the Windows
Store, snap, secure boot, and multitouch. If your PC doesn't support
one or more of these features you'll see a warning. You'll still be able
to install Windows 8, but specific features won't be available to you.
It provides the option to buy, download, and install Windows 8.
If your PC is ready to go, Upgrade Assistant provides a recommendation
on which edition to buy, and walks you through the steps to upgrade.
Edited by JerryW - 04 Nov 2012 at 1:45pm