MPC-HC is an extremely light-weight, open source media player for Windows. It supports all common video and audio file formats available for playback.

Media Player Classic – Home Cinema (MPC-HC) v1.6.8.7417 (Installer + Portable) | 7.1/7.6/9.1/9.9 MiB

Lightweight
Watch movies on any SSE CPU, even on your old computer back from '99.

Customizable
With its wide array of options, MPC-HC can be customized to fit almost any needs. Among other things we added custom toolbars.

All around player
MPC-HC can also be used as DVB player.