Nowadays Windows 8 is the hot topic among the operating system. Daily huge amount of the Windows lovers are upgrading their PC to Windows 8 OS. This latest operating system consists many new features like Apps, touch screen supports etc. If you have not still upgrade your PC to Windows 8, click here to know how to upgrade PC to Windows 8.Before that let's have a small look on what you will loss when you upgrade PC to Windows 8 OS. 
From windows 7
If you are upgrading your PC from Windows 7, there is no problem. All the personal files, apps and all the Windows settings will automatically get transferred to Windows 8 OS.

From Vista
If you are upgrading your PC from Vista, only Windows Settings and your Personal file will get transfer. And all the installed apps will never get transferred to Windows 8. You have to re-install the particular apps manually.

From XP 
If you are upgrading your PC from Windows XP, you will lose all the Windows settings and Apps. It only transfers the Personal files.

Windows 8 Release Preview
If you are upgrading your PC from Windows 8 Release Preview, it will transfer only your personal files. It will never transfer your windows settings and Apps etc...


Windows Consumer Preview or Windows Developer Preview 
When you transfer your PC to Windows 8 from Windows Consumer Preview or Windows Developer Preview. You will loss everything and you can get back all the personal files manually from Windows old folder.

Here I'll give a screen shot from Microsoft about this,