How do I clear the users from the log on drop down list?

I have serveral people that use the same system and they all have various user names paswords ect. but we are finding that when a different user sits down they are able to log on the the previous persons spark session because they can just click on the name from the drop down list. its there a way to clear the user name cache?

Not really. You can of course go to

C:\Documents and Settings\User\Application Data\Spark

or

C:\Users\User\AppData\Roaming\Spark

edit the spark.properties file and delete the saved logins/passwords every time you log out the Spark, but that’s not very convenient. Spark is just not designed for such type of usage.