Hi ,
Better Configure like this:
--------------------------------------
Machine 1
----------------
-ASP .Net Application [Web server]

MAchine 2
------------------
-SQL Server [Db Server]

Machine 3
------------------
-Load Generator [Vuser Generator]

MAchine 4
--------------------
-Probing Client [to minitor 1 user activity]

Better dont configure Webserver and database server in same machine.
Why bcose, we can not find out that which eat more resource .[like
%procossor time etc].

Second the Test-tool itself required a very good configuration to
generate load.So it should be in separate machine.[depends upon the
tool each Vuser reqd a specific amount of RAM]
Next you have to take care abt your N/W too.

Thanks and regards,
Sathyajith V K [India, Bangalore]