It is a temporary W(indows)A(ddress)B(ook). Comes from a Outlook Express update you applied from Microsoft lately. I understand a fix may come out in Windows 2525. No really I don't know what the plans are to fix this but now you know it is not something to fear. Just a pain. Why mine appears in C:\Program Files\Common Files\System\MAPI\1033 I have yet to figure out why.