Hi,
When I try to join a computer (Win XP-SP2) to the domain, a prompt comes up asking for the domain administrator credentials. Once I submit the credentials, I receive a message:

The computer cannot be joined to the domain"<domainname>"
Network path cannot be found

Please help me out as it has become very crucial for me to solve this.

Sai Ramana

If your server hasn't got your PCname it will not let you on.

e.g. computer name PC26

On the server there will be a list on PC names that are attached to the domain

That's what I have to do, if there are 2 names the same it will clash and not go on.
Also check you network setting a choose obtain ip settings

Actually, the computer account on the domain is created as part of the process of joining the domain - which is what Sai is trying to do.

First of all, make sure the Windows Firewall is turned off. In my experience, this is the most common cause of this error.
Second (if the first didn't solve the problem), make sure that the first DNS server setting on the workstation in question is set to the IP address of the DNS server for your domain (most likely the domain controller if it's a small network). You can either set this manually on the workstation, or alter the settings on your DHCP server to give this setting to all workstations (recommended).
The reason for this is that Windows XP (and probably Vista) gives preference to DNS address resolution over NetBIOS resolution, unlike previous version of Windows. So you can browse to the server, make a connection with it that asks for the admin user/pass, but once you try to do domain authentication protocols, communication will fail if it can't get DNS resolution. (This will also cause a host of other "weird" symptoms, like losing connection to printers that are shared off the server about 6 hours after logon. It took me about two weeks and lots of Googling to figure that one out the first time.)

Hope this helps!
Let me know if you need more details.