For information localized at the workplace (say, a screenshot for an error, etc.), linking this data directly to the work item is the way to go. For data whose lifespan exceeds its lifetime (knowledge base material, current documentation, etc.), consider sharepoint.
So, for your example, if a defect had some data that was localized and did not have a real long-term value, you will leave it in the workplace for historical reasons, but if it has a longer-term value, consider connecting it with Sharepoint (wiki or some other document) and, possibly, adding a link between the error (or another work item) and the sharepoint article (do this using the hyperlink link type).
Another option to search for some of these workitem related notes would be to use an extension (i.e. http://visualstudiogallery.msdn.microsoft.com/3f31bfff-5ecb-4e05-8356-04815851b8e7/ ), but IMO for material with long-term value, Sharepoint makes a lot more sense.
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