Equinix will replace Western Digital in the S&P MidCap 400

SAN FRANCISCO (MarketWatch) -- Hard drive developer Western Digital Corp. will replace data center services provider Embarq Corp. in the S&P 500 index, Standard & Poor's said late Thursday. Meanwhile Equinix Inc. will replace Western Digital in the S&P MidCap 400, Standard & Poor's said. Embarq is being acquired by CenturyTel Inc.