HTTP 500 Errors On IIS/XP Pro

I am getting this error while running any web page through IIS:
Server Application Error

The server has encountered an error while loading an application
during the processing of your request. Please refer to the event
log for more detail information. Please contact the server
administrator for assistance.

on the Event log i am getting this error:
---------------------------------------------------------------------------
---------
DCOM got error "Logon failure: unknown user name or bad
password. " and was unable to logon .IWAM_PS4433 in order to
run the server:
{3D14228D-FBE1-11D0-995D-00C04FD919C1}

and the following Warning Msg:
---------------------------------------------------------------------------
-------
The server failed to load
application '/LM/W3SVC/1/ROOT/IISHELP'. The error was 'The
server process could not be started because the configured
identity is incorrect. Check the username and password.
'.
For additional information specific to this message please visit
the Microsoft Online Support site located at:
[url]

For more information, see Help and Support Center at
[url]