we are useing sqlserver 2008
i have one login dttl has sysadmin rights for which i want to enable audit log for every thing which is done by this user
i dont want to enable it for all the logins
Depending on what version of SQL 2008 you are using depends on whether you'll be able to use Steve's suggestion. Only Enterprise (and developer) have the audit features. Otherwise you could setup a server side trace and set a filter on that user alone. You can set it to trace any events you want.
You might look into these commands: