What codec do I need?

I'm trying to import a .avi file onto Windows Movie Maker but it keeps saying that it "cannot be imported because the codec required to play the file is not installed on your computer. If you have already tried to download and install the codec, close and restart Windows Movie Maker, and then try to import the file again."
It doesn't tell me what codec I need and I've restarted it umpteen times and I get the same error. does anyone know what the problem is?

you can use k-lite codec, search it in google for download.

I'd recommend the Combined Community Codec Pack over K-Lite. Get K-Lite too, though, for the Real alternative codecs.Oh, and you might also want CoreAVC. It's better for H.264 decoding than ffdshow (ie it's easy on your computer), which comes with CCCP, but you "have to pay" ;)

It still shows the same error.

you already download the k-lite codec? or any codec like tehuber said?

I use Ace mega codecs pack myself, and it comes with a program called 'g-spot' that can identify codecs used in video files.

I don't believe K-Lite ships with Real. I believe I had to get mine separately. One that worked anyway.

It's CCCP that doesn't have Real. K-Lite has it.