Encarta appears to be a discontinued product, so there is not likely to be much more in 2009 than was in 2008.
You could install Encarta in a Virtual Machine if you don't want to uninstall 2008.
Windows Virtual PC
Download Windows XP Mode
http://www.microsoft.com/windows/virtual-pc/download.aspx
Windows XP Mode (Windows 7 only, but not any of the Home versions) "You are not eligible to download Windows XP Mode. You must have Windows 7 Professional, Enterprise, or Ultimate to run Windows XP Mode". If you have an old XP CD (or other older Windows CD) available you can just download the Virtual Machine and skip the XP Mode download.
This covers the whole gambit of virtual machines in "Home" versions if you want to have a look at it. Of course you will need a licensed copy of XP to install and run in any of them (except XP Mode).
VirtualBox is an impressive VM contender