You might be surprised to know that Microsoft is ready with Windows 7 beta build 7004 (7004.0.081203-1830) which is known to be compiled on December 3, 2008, well the date is pretty contradictory with Windows 7 beta 1 build 7000 said to be compiled on December 12, 2008.
Microsoft’s Director of Development and Platform Strategy, Scott Wylie, wrote on his blog today about his experience with what he called a “pre-beta” build of Windows 7 - build 7004 and also included a screenshot. There isn’t much to see other than the Live Mesh icons and the new build number. The Windows community had previously speculated that the Beta 1 build would be 7000.0.081212-1400, so this has certainly caused some confusion.

According to WinFuture.de, this build was compiled at December the 3rd, which was before build 7000 which was compiled on December the 12th. Neowin states that Microsoft employees were given access to this build earlier this week.
From what is gathered so far despite the confusing post from Steve, Build 7000 is to be Beta 1, and Build 7004 is the next branch that starts for the RTM/RC phase.

Interestingly, Scott Wylie has pulled the article off his blog, suggesting that he might have revealed something that he shouldn’t have.

“I like the new taskbar which combines the old Quick Launch with running apps. I wish I had more control over icon size - still not big enough on my 1400 x 1050 screen to my eye. I love the fact that at long last I can change the order of running tasks on the task bar! I'm one of the small number of people who uses the auto-hide feature of the taskbar (in Vista I used a two story taskbar with Quick Launch along the top and running apps below) to provide more real estate. I'm finding this doesn't look so great with Win7 and have reverted to fixed single story. Apart from an issue where my default window color changes from transparent to black if I click on a desktop icon (maybe my video card?) I haven't encountered any problems,” Wylie added. More Go To http://software.intel.com/en-us/blogs/2008/12/19/windows-7-pre-beta-build-7004/ & http://www.mydigitallife.info/2009/01/05/windows-7-build-7004-is-win7-beta-2/
Windows 7 Build 7004 Is Windows 7 Beta 2 Windows7prebetabuild700ru0