Microsoft will stop MOSS 2007 and WSS 3.0 without Service Pack 1 support tomorrow January the 13th 2009. So in order to get support from Microsoft you need to install at least Service Pack 1.
Source: http://support.microsoft.com/gp/lifesupsps#Office
How can I check the current version of MOSS 2007 and WSS 3.0?
The version number of Service Pack 1 is 12.0.0.6219. You can check this by open up Central Administration. Go to the operations tab.
After that go to Servers in farm.
The version number of my SharePoint installation comes from the December Cumulative Update which is greater than 12.0.0.6219 and therefore my installation is still supported by Microsoft. :)