Download K-Lite Mega Codec Pack here:
http://www.free-codecs.com/download/k_lite_Mega_Codec_Pack.htm
This codec pack probably has all the codecs you need to make things work.
- If file types like WMA and DAT work, then it's definitely a codec issue. Reinstall the codec. (Uninstall completely first, restart and install)
- If you cant play ANY video format, its got to be your VGA driver or a courrupt Windows file in which case you'll have to reinstall Windows
- If you did both of these, try restoring default settings in your BIOS. If that also doesnt work, then you'll have to get your VGA checked. Or even your motherboard. (It shouldnt come this far... I'm pretty sure its something small)
Hope this helps! Good luck machang!