Windows 7 x64 Home Premium

What You Need to Run Windows 7 Home Premium:

1 gigahertz (GHz) or faster 32-bit or 64-bit processor. More about 32-bit vs. 64 bit computers.
1 gigabyte (GB) RAM (32-bit) or 2 GB RAM (64-bit). What is RAM?
16 GB available hard disk space for 32-bit computers or 20 GB for 64-bit.
DirectX 9 graphics device and driver. How to install DirectX graphics devices.
What You Get With Windows 7 Home Premium:

The Aero Desktop, Windows 7's look and feel.
Windows Search, which is useful for finding things on your computer.
HomeGroup, which is a networking technology for sharing files, printers, music and other stuff with other Windows 7 computers.
Windows Media Center, for organizing your music, movies, television shows and so on.
What Windows 7 Home Premium Does Not Have:

Windows 7 Home Premium lacks a few security features like file and hard drive encryption. It also doesn't have the problem steps recorder, a great troubleshooting tool. The most important feature not found on this edition, however, is Windows XP Mode. XP Mode ensures backwards compatibility -- in other words, programs that ran under Windows XP will run just as well within Windows 7.

One other factor you may want to consider is that Windows 7 Home Premium can't join a domain, so businesses will want to look at a higher-level version.

Why Choose Windows 7 Home Premium:

The average user or family will find most everything they need with Windows 7 Home Premium. It's a good choice for non-technical users, and those who don't need it to connect to a work network. This will satisfy the large majority of users.

If you can live with the security and compatibility limitations, the relatively inexpensive Windows 7 Home Premium is a good choice. Consider carefully before you buy, however.