You have a Microsoft Office SharePoint Server 2007 Service Pack 1 (SP1) server farm.

All servers in the farm run the 64-bit version of windows server 2003 Service Pack 2 (SP2).

You plan to perform an in-place upgrade to SharePoint Server 2010.

You need to ensure that you can successfully run the SharePoint Server 2010 Pre-Upgrade Checker.

What should you do?

A.
Install Windows PowerShell 2.0 on all servers in the farm.

B.
From Central Administration, select the Quiesce farm option.

C.
Upgrade all SharePoint servers to Windows Server 2008 and install Microsoft .NET Framework 4.0.

D.
Install Windows SharePoint Services 3.0 Service Pack 2 (SP2) and SharePoint Server 2007 SP2 on all SharePoint servers.

Explanation:
In order to run the Pre-Upgrade Checker, SharePoint 2007 Service Pack 2 (SP2) MUST be installed.

Run the pre-upgrade checker (SharePoint Server 2010)
http://technet.microsoft.com/en-us/library/cc262231.aspx