That's right... they're evil. They can seriously mess up your system and there's no reason to use them! Ever.

Unless it is CCCP, which stands for Combined Community Codec Pack. This is the only codec pack you should ever use.

The K-Lite Codec Pack is pretty well known. Maybe not for the best reasons either. It contains an illegal version of DivX (since you're supposed to pay for the encoder), DivX ;-) (well known as a hack of the early Microsoft MPEG-4 codec), an XviD codec, x264, and ffdshow... amongst a few others.

How many MPEG-4 decoders do you need? The DivX decoder will decode XviD. The XviD decoder will decode DivX. The 3ivX decoder can decode DivX and XviD. ffdshow can decode DivX and Xvid and more. So, ffdshow, DivX, XviD and 3ivX all can decode the same video formats. Having all 4 installed at once can seriously confuse Windows!

Then there's all the different MPEG-2 decoders you could install - you only need one, and there are 5 included, 3 of which are illegal. The Elecard decoder is especially bad, since it can stop you being able to view DVDs completely if you're unlucky.

Not even uninstalling K-Lite will fix the mess it makes, it may require a format. Is it really worth it?

So what can you do instead of installing an evil codec pack?
Download and install CCCP.

It's built around ffdshow, ffdshow is open source, totally free, and will decode DivX, XviD and much more all without needing all those pirated decoders. CCCP will install only what you need, and will configure everything without breaking your PC.

So avoid the headaches and stress. Steer well clear of evil codec packs. Your system will thank you.