When I click on the video, "the selected file cannot be played because your system does not have the required compresser/decompresser (codec) installed. Click here for more info. It takes me back to load the Quick Time, which I already did & installed. forgot to mention this is PSE 7
The first thing that I would do would be to check that you have the latest version of Apple Quick Time installed.
Next, I would get the great, free utility, G-SPOT, and run the file(s) through that. It will give you the full details on the CODEC, if it can read that data. Then, you know what you are looking for. I'd Google that CODEC, and try to find it from the source, say Apple, Lead, MainConcept, Morgan, etc., rather than go for free CODEC's, or any CODEC "packs."
Also, tell us what kind of camcorder this video came from and how you got it into your computer.
Most video from Flip and other pocket cams as well as video from still cameras will need to be converted to a more standard video format before you can edit it in Premiere Elements.