Summary: I could not get the card to work properly on Windows 8.1 x64. Intel has stated it is only offering "In Box Support" for this card - not full support - which means drivers downloaded from their site will *not* work under Windows 8.1. (Windows 8.0 is okay.
Summary: The headline says it all. Windows XP gave constant error messages. Windows 7 had delays in all phases of networking but no error messages. Replaced it with an older card from an obsolete PC and now have a fast connection.