First off, I wouldn't proclaim to the masses that you downloaded an illegal copy of Matrix Reloaded.
Secondly, try the K-Lite Codec Pack. It has codecs for everything, including AC3, and its AC3 codec actually works! http://www.k-litecodecpack.com
Thirdly, it sounds like your hard drive is dying. If it is still under warranty, get it repaired/replaced or start shopping for a new HDD.
No, I like women.