Slow, But Successful Network Logins

I have a couple of PCs on my Windows2003 network (workstations running XP Pro) that log in very slooowly. After entering the ID and password, the window dims and hangs for about two minutes or so, then goes ahead and completes the login. This user is on a notebook and tells me that when logging in at home (not on the network) the process proceeds normally without delay. I have checked for viruses run SpyBot and AdAware, but nothing seems to impact this problem. I can’t really correlate this problem with any sort of patch update or anything like that.

How can I find out what’s going on “behind the screens” that is taking so long? Thanks in advance for any help you can provide-