Is there a way to delete old data from the database if it's using MS SQL Server?

 

I tried using the reinitialize.bat script, however this seems to be looking for a MySQL database.

 

I'm using SQL 2008 Express Edition, and my Applications Manager database has reached 4 GB which is the limit on this version of SQL - hence I need to purge the old data. I'm not bothered about keeping any of the existing data, I'd really like to start from scratch if possible?