The express products are "real" VS Products as they provide functionality similiar to that of Visual Studio. They are not evaluation copies but you do have to register with Microsoft to activate the product. Obviously, the Express products lack features that are found in the full version of VS2005 (although i can not tell you exactly which features are absent in the express editions)
Depending on your needs the express products should work for you. hth.
Read this if you want to know how to get a correct reply for your question:
^^Took that from planoie's profile^^
^^Modified text taken from gbianchi profile^^
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