re: question 2...

I strongly recommend the Cole2k Codecs,

A link for the download is in my signature below.

You may have read numerous posts with people touting their favourite CODEC 'Packs'... I recommend the Cole2k Codecs
because they work, the installation is very simple and... AND, the entire pack is VERY easy to REMOVE... This is in great contrast to the majority of CODEC Packs I have ever tried.

If you try my suggestion, be sure to download ONLY the STANDARD version.
Also, do the simple or 'easy' install, NOT the expert... And, no, you do not need the Cole2k Toolbar !!!

Let us know how it goes.

p.s. I'm not the only one who has experienced this... Many times when 'previewing' a video file during download 'something' happens and although the preview seems to be OK, when the D/L has finished there are problems with the file... Apparently because of the action of previewing !
Only with vid files... Not music. No, I still don't know why !

__________________
Fusion for REAL!--CDex 1.51--Wackyuses--Bitzi - Check Files Before Download !--.mp3 File Name Change Problems? Try Rename-It!--Alternate PORTS--Avast- Anti-Virus--WindowWasher--IrfanView--PC Pitstop - Test your PC !--Mac OSX Troubleshooting--GO .ape ! - For 'Lossless' Audio Compression--Port :6346 - Test If It Is 'Blocked'--Cole2k Codecs--OldVersion - Newer isn't always better !
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Tomorrow's forecast:
Sunni in places, Shi'ite in others...

I do appreciate your willingness to help but, Cole2k Codec does not do anything for the ability to preview .avi. At least , not for my computer.