Just like Windows 7, Microsoft Office 2010 is also available for trail download from Microsoft website. You can install the downloaded full featured trail version without any CD / product key and use it for 30 days evaluation period before mandatory activation would be required.
However just like Windows 7, you can rearm or reset the evaluation period of MS Office 2010 too.
How to reset / rearm the trail period of MS (Microsoft) Office 2010 for without activation use of upto 6 months ?
After running out of initial 30 days of evaluation, head down to the below mentioned directory
C:\Program Files\Common Files\microsoft shared\OfficeSoftwareProtectionPlatform\
or
C:\Program Files (x86)\Common Files\microsoft shared\OfficeSoftwareProtectionPlatform\
to run a file (with administrative privilege) called OSPPREARM.EXE.
This option can be performed a maximum of 5 times, allowing you upto 6 months of free evaluation of the product without the activation.