Lately, the files that I download started going slow. Like, when the file is playing, the video goes slower than how it's supposed to for about a split second to two seconds. I thought it was only because the files were too large and my computer couldn't keep up with it, but it only happens to the new files that I download. The files that I already had and are larger than my new ones and are better quality work fine. Also, there is this one file that I recently downloaded that is really bad quality and the file goes the slowest. I tried downloading the newest K-Lite Mega Codec Pack, but the problem persists. Also, if I try to play anything on Media Player Classic that is good quality, the file pauses every few seconds. Help, please?

You didnt write what files they are.

When the older files are working and you didnt change anything on your pc, the problem lays in the new ones.

Are the new files a different format than the older ones ?

Try checking them with "G-Spot".

Open the files with it and see if the codecs are installed or not.

Also it shows what files they are.

Another option, try to open it with VLC Player. Plays nearly everything.

Like I said before, would be good to know what kind of filesthey are.