"DNS suffixes" are used for resolving unqualified domain names (names with no dots).
In the Windows Control Panel, double-click the "Network and Dial-up Connections" (or "Network Connections" on Windows XP / 2003) icon:
Right-click a network connection icon and select "Properties" from the pop-up menu:
In the network connection Properties dialgo, select "Internet Protocol (TCP/IP)" and click the "Properties" button:
In the "Internet Protocol (TCP/IP) Properties" dialog, click the "Advanced..." button:
In the "Advanced TCP/IP Settings" dialog, select the "DNS" tab, and specify which DNS suffixes to use for resolving unqualified domain names:
If you choose the first (and default) option to append primary and connection specific DNS suffixes, then you will also need to configure the primary DNS suffix. See reference articles below.