You need to put a packet sniffer like Wireshark or Microsoft Network Monitor 3.1 on one or both ends of the conversation. This will show you what is happening on the wire during the login process. Otherwise you will be “shooting in the dark”. Once you get that information, you can either post more information about the findings or solve the problems based on your discovery
*** Improved by Wrobinson on St. Patrick’s Day 2008 ***
It does not hurt to look at the network but I would start looking at things such as free disk space, size of the roaming profile if roaming profiles are in use; also, the possibility that the profile is corrupted. Does the computer take as long for all users that log on to it, or specific user(s)? You should also look into group policies being applied to the computer, any login scripts which could be hanging and so on. You also want to make sure that there is a domain controller and global catalog in the same site as the computer. Something else to lookout for is time synchronization.
***reply by labnuke99***
ahhh yes… the old roaming or corrupted profile transfer issue. It is true that this may be causing the slow login issue. It’s not clear whether this is for one or multiple clients.