To check which logins have denied access to SQL Server.

To check LOGINS which have denied access to SQL SERVER 2005/2008/2008 R2

select name,denylogin from sys.syslogins where denylogin ='1' 


To check LOGINS which have denied access to SQL SERVER 2000.


select name,denylogin from syslogins where denylogin = '1'