logs in Event viewer

i have a windows 2000 proff pc, each time i try to logon to windows 2000 domain, i am getting the following logs in event viewer

Application log:-

Event Type: Error
Event Source: Userenv
Event Category: None
Event ID: 1000
User: NT AUTHORITY\SYSTEM
Description:
Windows cannot determine the user or computer name. Return value (1722).

system :-
Event Type: Warning
Event Source: w32time
Event Category: None
Event ID: 54
User: N/A
Description:
The Windows Time Service was not able to find a Domain Controller. A time and date update was not possible.
Data:
0000: 91 05 00 00 ?…

pls tell me where is the problem and the solution