With “Bluestacks App Player”, a free tool, Android mobile apps can be used under Windows 7, Windows Vista and XP. Bluestacks, easy to download and install, is a virtual PC on which the apps run.
More than 400,000 apps can be used, with a few (e.g. Evernote, RSS-Reader Pulse) pre-installed. More can be downloaded via GetJar, 1Mobile or Amazon.
One weakness of the system is that there are occasional disruptions in graphics-intensive games. However, this problem has already been addressed and is to be remedied.
Bluestacks is also available in a paid version after the beta version expires. It is then possible to download paid apps and a synchronization between the program and the smartphone with Android is possible. Furthermore, however, a free basic version should be downloaded.
Download Bluestacks App Player (Beta): http://bluestacks.com/