Not knowing about Windows 8 and its Metro UI is only possible if you are living in caves. If you have tested either Windows 8 consumer preview or release preview then you would notice that it has replaced good start menu and start orb with charm bar. The Windows 8 Charm bar is accessible by hovering your mouse over at the bottom left corner of screen, which brings application specific or general configuration menu.
Now if you are reluctant to download GBs of ISO image file and install Windows 8 and still want to test new features of Windows 8 then here is small app, mStartEX for you. mStartEX is Windows 8 style start menu replacement for Windows 7, Vista, Xp. It aims to provide Windows 8 start menu experience on older operating system.
mStartEX come in free as well as paid pro version, being in beta mode pro version is available at ridiculously cheap price ($1.25). Since mStartEX is still being developed, it may contain bugs or may not work as expected.
The free version of mStartEX comes with pretty much all the features of pro version except full screen mode and invisible mode. Though not exact replica of Windows 8 Start menu but mStartEX emulates exactly like Windows 8 start menu. mStartEX offers hot corner activated popup menu, option to change icons, background tiles, user avatar, change hover effect or customize move over tile effect and much more.
mStartEX is available in the form of web installer or setup file. mStartEX download and installer will always get you latest version available for download. You can follow the tutorial mean while it downloads and installs mStartEX start menu.
You will be presented with setting screens at first run, you can choose to customize or let it run in default mode. You can adjust screen alignment to left or right, under titles setting you can chose the style of icon as you want. Settings for the orb style is present under corner settings.
Every time when you hover your mouse over mStartEX orb, mStartEX menu will be activated. You can also add metro style clock to desktop from settings tab.
At the moment mStartEX is far from what actual Windows 8 Metro menu, also it is still in beta development and often throws errors and exceptions. But at the end it is free to use and one step close metro style menu.