How to upgrade Windows 7 home premium to professional? Please help me.

Hi, I bought a Dell desktop computer and it came with Windows 7 Home Premium 64 bit. One of my friend told me that the Windows 7 Professional has more features than Home Premium edition.

And I would like to know how to upgrade from Windows 7 home premium to Windows 7 professional edition? Also, I want to make sure that it keeps my applications and settings intact on my PC.

Your help in this regard would be highly appreciated.