The first thing you will probably need for using 4GB or more of RAM is a [shift to 64-bit OS][1].

Beyond that,

- [Virtual Machines][2] 
- [Visual Studio][3], [then][4] and [now][5]


  [1]: http://www.codinghorror.com/blog/archives/000811.html
  [2]: http://vmtimes.com/2009/06/can-we-run-a-64-bit-operating-system-on-a-virtual-machine-running-on-an-x86-based-machine/
  [3]: http://blogs.msdn.com/andypennell/archive/2004/01/22/61943.aspx
  [4]: http://visualstudiomagazine.com/articles/2005/06/01/how-does-x64-measure-up.aspx
  [5]: http://stevenharman.net/blog/archive/2008/04/29/hacking-visual-studio-to-use-more-than-2gigabytes-of-memory.aspx