The values in sysstat refer to what type of object it is. 3 means it's a user table. But I would advise against using this column in your scripts, because first of all in SQL 2005 you should work with sys. objects which doesn't have a sysstat column and second Microsoft can change the values in a future version.

The proper way of checking it is a user table would be using the OBJECTPROPERTY function.

IF EXISTS (SELECT * FROM sys.objects WHERE name ='mytbl'

AND OBJECTPROPERTY(OBJECT_ID('dbo.mytbl'),'IsUserTable')=1)

DROP TABLE dbo.mytbl