The reason behind this problem has to do with another software you had installed which probably messed up your registry file containing the features you mentioned. Although the markers are enabled by default in Visual Studio 2008 there is a way to add, create, edit and implement those markers if they have been turned off. For a proper and clear explanation of the problem and a solution to your request please visit this link which explains entirely how to implement markers and how to turn them on. You should bookmark that page for future use in case something gets broken again.
