Can someone please tell me where I can find the official codecs for movie maker?

I'm trying to import a .wmv file, but get this error:
001.wmv could not be imported. The required codec was not downloaded automatically because the Download codecs automatically check box is not selected in the Options dialog box.
I selected the check box and was able to import the file, but since I did that movie maker crashed regularly, and my computer went to a crawl.
After running my security software, I discovered my computer had been infiltrated. I removed the threats, but found my computer did not perform as it did before, and movie maker continued to crash. So I started with a fresh OS. I don't want to go through the same drama, by allowing the automatic codec download. So I would like to know where I can download the genuine codecs.
Thanks