Only 1 network adapter can be enabled on the PC joining the domain, and preferably a wired connection. If any others exist such as a wireless card, disable until domain joined. On occasion Bluetooth adapters will also conflict, so I recommend disabling them as well.
Configure the connecting PC’s network adapter either statically or through DHCP to point ONLY to the domain controller at the corporate office for DNS. Do not add an alternate external DNS server such as an ISP or router as these will often respond first and name resolution will fail.
In the NIC configuration, under Internet Protocol Version 4 (TCP/IPv4) properties, click advanced, and under the DNS tab insert the corporate internal DNS suffix, such as CompanyDomain.local in the box entitled "DNS suffix for this connection"
Then join the domain using the traditional method of Computer (formerly My Computer) | Properties | Change Settings | Change | enter the internal domain name | click OK | and you should be prompted for credentials for an account authorized to do so, a Domain Admin account. If the Domain Controller is a version of Small Business Server the SBS option to use http://SBSname/connectcomputer or http://connect most often will not work. (more detail and screen shots for the joining the domain process can be found below in the using a VPN client section).