tr2012

Honorable
Aug 26, 2012
62
0
10,630
Control Panel > System and Security > System > Computer name, domain and workgroup settings > Change Settings > Change button > (select Domain radio button and add domain name) Click OK > enter credentials of a user allowed to add computers to the domain.

Reboot when prompted

This of course is assuming you're running Win 7 Pro or higher, lower versions cannot join a domain.