What is the real difference between Windows 7 home edition 64 bit vs Professional edition 64 bit?

Windows 7 Home Premium:

Home Premium will be the edition that an overwhelming majority of computer users in the United States will choose, mostly because it will come pre-installed on new computers after the October 22nd release of Windows 7. This edition comes with all of the desktop enhancements that Windows 7 has to offer, including Windows Aero, Flip 3D, Live Thumbnails, and the ability to customize all aspects of the user interface.

Windows 7 Home Premium comes with all of the multimedia features, such as Windows Media Center, DVD Maker, Windows Media Player, and all of the games that Windows 7 has to offer. Windows Mobility Center is also included, which provides advanced features for laptop and portable devices as well as touch input and multi-touch functionality.

If you are an average to above-average computer user who will use this product in a home or home business setting, this is most likely the edition that you will want. It is priced right at $120 for an upgrade version for current users of Windows XP or Vista and it will definitely run on any computer that decently runs XP and Vista right now.

Windows 7 Professional:

Users of Windows 7 Professional will be small to mid-size businesses and companies who need advanced networking features, such as Active Directory and domain log-in support. Professional also offers network backup, an Encrypting File System (EFS), and the ability to connect to and control a remote PC via Remote Desktop. XP Mode is also available to Professional edition users, which allows users to install and run applications that only work in Windows XP in a seamless Windows 7 environment.

The biggest two questions of whether or not you need Windows 7 Professional are the following: Do you need domain support and do you need seamless backward compatibility for legacy Windows XP applications?

Windows 7 Ultimate:

This edition is for the power-user and computer enthusiast. It includes every single available Windows 7 feature, but is still relatively similar to the Professional edition. Windows 7 Ultimate gives users access to BitLocker and BitLocker To Go, which is a drive encryption system for the system hard drive and portable media, like a USB thumbdrive. Home users will not need any of these more advanced features and the price of $100 extra is most likely not worth spending for it.

32-Bit vs. 64-Bit:

Most of the Windows 7 product editions ship in both 32-bit and 64-bit flavors in the retail package. Users purchasing new PCs will be given a choice of either 32 or 64 bit operating systems at their time of purchase. There are no cosmetic or functionality differences between 32 and 64 bit, but there is one small under-the-hood different. The 64-bit versions of Windows 7 support either 16GB or 192GB of RAM, while the 32-bit editions only support a maximum of 4GB. All new and relatively new CPU's are 64-bit compatible and users should almost always choose 64-bit versions of Windows 7.