I have got this error while trying to install SharePoint 2013
What is Max Degree of Parallelism ?
When an instance of SQL Server runs on a computer that has more than one microprocessor or CPU, it detects the best degree of parallelism, that is, the number of processors employed to run a single statement, for each parallel plan execution. You can use the max degree of parallelism option to limit the number of processors to use in parallel plan execution. SQL Server considers parallel execution plans for queries, index data definition language (DDL) operations, and static and keyset-driven cursor population.
Read this for more details http://technet.microsoft.com/en-us/library/ms189094.aspx
How to fix it ?
Open Microsoft SQL Server Management Studio
Login with sysadmin user
Right Click on instance name and select properties >> Advanced
To access a SQL Server instance through a firewall, you must configure the firewall on the computer that is running SQL Server to allow access. Any ports that you manually assign must be open in Windows Firewall.
To configure Windows Firewall to open manually assigned ports
Verify that the user account that is performing this procedure is a member of either the sysadmin or the serveradmin fixed server role.
In Control Panel, open System and Security.
Click Windows Firewall, and then click Advanced Settings to open the Windows Firewall with Advanced Security dialog box.
In the navigation pane, click Inbound Rules to display the available options in the Actions pane.
Click New Rule to open the New Inbound Rule Wizard.
You can configure the Internet Protocol security (IPsec) to help secure communication to and from your computer that is running SQL Server by configuring the Windows firewall. You do this by selecting Connection Security Rules in the navigation pane of the Windows Firewall with Advanced Security dialog box.