Update to a newer version of OS X from OS X 10.6.8 Every time I click Software Update it tells me there's no new software! I don't even know what software I'm running so I can't search for updated software. Why is it stuck on 10.6.8?
As others have mentioned, Lion (10.7) is the latest version of OS X supported by your machine. Although it's no longer available for download from the App Store, you can still order the media from the Apple Store.