Back in April, Mariano Szklanny posted a tip on how to get intellisense in VS when editing the XML for a work item type.

If you’re editing work item types, you will find useful having Intellisense in Visual Studio 2005:

1. Open the Visual Studio Team System Integration folder from the VS 2005 SDK. The SDK can be downloaded from here.
2. Navigate to Work Item Tracking.
3. Copy the file WorkItemTypeDefinition.xsd included in Work Item Tracking Schemas.zip to “C:Program FilesMicrosoft Visual Studio 8XmlSchemas”, supposing you installed VS 2005 in the default location.