Effective January 2011, the IEEE has changed its official policy regarding what versions of their articles published in IEEE journals and conference proceedings may be posted on author websites and in institutional repository. According to Kenneth Moore, Director, IEEE Book and Information Services, authors may post to their personal websites or to an institutional repository any pre-print version or the accepted, peer- reviewed version, just not the final IEEE published PDF. In addition, this policy is not retroactive. So any IEEE papers posted to websites and IRs prior to January 2011 do not have to be removed.
You can read more about the policy here: