Microsoft Security Essentials Microsoft's real-time free antivirus and spyware protection suite.
K-Lite Codec Pack Full Comprehensive selection of video codecs which allow for the playback of most types of video files found on the web including DivX, XviD, MKV, MusePack DirectShow.
K-Lite Codec Pack Standard Free collection of high definition video and audio codecs including DirectShow video decoding filters and MPC-HC player.