Download Windows 8 Upgrade Assistant

Microsoft recommend customers to download and run the Windows 8 Upgrade Assistant before upgrading to Windows 8. This tool scans your current PC to check whether it is ready for Windows 8 and then provides a compatibility report and optional steps for you to buy, download, and install Windows 8.

Windows 8 Upgrade Assistant is the best way to tell if your hardware, apps, and connected devices are ready to upgrade to Windows 8. It is available for free and can be download from Microsoft Download Center here: Window 8 Upgrade Assistant

Notes:

• You can run Upgrade Assistant without purchasing or installing Windows 8.
• To check if your peripheral devices like printers or monitors will work with Windows 8, be sure they're plugged in and connected to your PC before you run Upgrade Assistant.

What does Windows 8 Upgrade Assistant do?
There are four main things that Windows 8 Upgrade Assistant does:

1. 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.
2. 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.
3. 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.
4. 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.

Windows 8 System Requirements
Windows 8 works great on most of the same hardware that runs Windows 7. Here is the full system requirements for Windows 8:

• Processor: 1 gigahertz (GHz) or faster with support for PAE, NX, and SSE2
• RAM: 1 gigabyte (GB) (32-bit) or 2 GB (64-bit)
• Hard disk space: 16 GB (32-bit) or 20 GB (64-bit)
• Graphics card: Microsoft DirectX 9 graphics device with WDDM driver

Additional requirements to use certain features:

• To use touch, you need a tablet or a monitor that supports multitouch
• To access the Windows Store and to download and run apps, you need an active Internet connection and a screen resolution of at least 1024 x 768
• To snap apps, you need a screen resolution of at least 1366 x 768
• Internet access (ISP fees might apply)
• Secure boot requires firmware that supports UEFI v2.3.1 Errata B and has the Microsoft Windows Certification Authority in the UEFI signature database
• Some games and programs might require a graphics card compatible with DirectX 10 or higher for optimal performance
• Microsoft account required for some features
• Watching DVDs requires separate playback software
• Windows Media Center license sold separately
• BitLocker To Go requires a USB flash drive (Windows 8 Pro only)
• BitLocker requires either Trusted Platform Module (TPM) 1.2 or a USB flash drive (Windows 8 Pro only)
• Client Hyper-V requires a 64-bit system with second level address translation (SLAT) capabilities and additional 2 GB of RAM (Windows 8 Pro only)
• A TV tuner is required to play and record live TV in Windows Media Center (Windows 8 Pro Pack and Windows 8 Media Center Pack only)
• Free Internet TV content varies by geography, some content might require additional fees (Windows 8 Pro Pack and Windows 8 Media Center Pack only)

Reference:
Microsoft
Softpedia