View Remote Desktop access logs on Win 2003
Solution 1:
Look in the Security Event Log for a Logon/Logoff Event 528, Logon Type 10
You can also setup an Audit Policy using the Group Policy editor to log logon success and failures. Go to Run and type gpedit.msc
Local Computer Policy -> Computer Configuration -> Windows Settings -> Security Settings -> Local Policies -> Audit Policies -> Audit logon events. Right click and select properties. Configure as you like.
Solution 2:
If you don't already have account logon events audited, then turning it on is not going to help you determine who has logged on to the server already. Turning on account logon auditing will help you in the future.
As far as RDP connections are concerned, there's no specific logging for that.