Note : Try these on a virtual platform before actually you implement them real time.
You can audit logon events on the server..do the following steps
on ya server
Start -> Admin tools ->Domain Security Policies
In the domain security settings window,
Expand Local policies and then audit policies.
now, double click on audit account logon events.It takes you to the properties page.
check 'Define these policy settings' and choose success or failure or both.
u now need to activate this gpo setting.
start->run-> type in gpupdate /force.
Now try logging on to your server from any of the clients.
to view logon events, goto event viewer under admin tools.
Play around with it.it should work..