In order to exploit all the features offered by Windows server 2008 at their full administrators would want to raise forest functional level of the forest. This ensures that administrators can configure their domain and forest environment to best fit the requirements of the organization. However before raising functional level of the forest administrators need to ensure that domain functional level of every domain in the forest has been raised up to the level at which administrators are planning to raise the forest functional level. For example if administrators want to raise the forest functional level to Windows server 2008 mode they need to ensure that domain functional levels of every domain in the forest are raised to Windows server 2008 mode as well. As an administrator if you want to raise the forest functional level you need to follow the steps given below:
1. Ensure that you are logged on to forest root domain controller with the credentials of enterprise admin.
2. Click on Start button and go to Administrative Tools.
3. From the appeared menu go to Active Directory Domains and Trusts and from the opened snap-in right click on Active Directory Domains and Trusts to get the menu.
4. From the available options click on Raise Forest Functional Level and on the appeared box from the drop-down list choose the appropriate functional level for the forest as per the requirements.
5. Click on Raise button and on the appeared box click on Yes button.
6. On the confirmation box click on Ok button and close Active Directory Domains and Trusts snap-in.