Is it possible to install a MS SQL Express Studio, where the studio tool also is included?
You are probably better off with the newer version of Management Studio Express (which will work against 2008 R2, 2008 and 2005):

http://www.microsoft.com/download/en/details.aspx?id=22985

The reason is that if you use the 2008 version and try to manage a 2008 R2 instance, for example, you may run into issues. Always better to have the client tools >= the highest version of the engine that you need to support.

Note that Management Studio Express is missing some of the SSMS functionality, such as managing agent, so if you have to manage other editions you may be better off investing $49 (or less, depending on vendor) into developer edition, which comes with the full version of SSMS:

http://bit.ly/oPq7NY