Technically, the previous poster is correct. If you try to download and install Mountain Lion from the App Store, it will not run, as this model is unsupported. With a bit of work, however, you can run Mountain Lion on these models. I had given a detailed answer to someone who received an error when trying to install Mountain Lion earlier; please read that for more details, or leave a comment, and I'll explain how to upgrade for you as well.
yes you can but.... it'll take some effort on your part. you'll need to upgrade the RAM to a minimum of 2GB. once that's done it will install. getting the installer for ML might be a bit tough but it will do it.