This topic is too sensitive to rely on third party tools. However, I recommend following Microsoft's instructions. There are also third party tools that allow you to rearm Office 2010.
Most of these articles were written before Office 2010 was released. You will find some complicated instructions on the Web of how to rearm Office 2010. If you rearm Office right before you create the OS master image, you can be sure that you have the full 25 days before users will bothered with Office activation notifications or before the retail edition goes into Reduced Functionality Mode after 30 days. This features allows you reset the grace timer to 30 days grace. This is where Office 2010 rearm comes in. You also have to take into account that it might take some time until Office finds a KMS host or until you activate it manually. If you have to perform other configurations before you create the master image, then it is quite possible that 25 days is too short. The grace period begins immediately after you installed Office 2010 on your master PC. However, it might be difficult to activate Office 2010 during the grace period if you deploy a pre-installed Office with an OS image. Either way shouldn't be doable within 25 days after the installation.
You can use the latest version of the Key Management Host (KMS) or activate Office 2010 with VAMT.
