Older mpg files

[johnt]

I have an odd problem with older mpg files (like a couple of years old). When I play them, I get pops and screeches, and sometimes brief video freezes.
It's not the source files, as they used to play fine, and play without problems on other PCs. If I re-encode the actual 'faulty' files (using TMPGEnc Express), they also play fine.
My guess is that there is some problem with the backward compatibility of whatever codec is used in the playback of these MPG files (same problem in both Winamp and Media Player).
I have tried removing and reinstalling several codecs (why won't the Microsoft MPG-4 codec go away under Windows XP when I remove it?).
My AVI files play fine, and all recent MPG files are OK too.
My questions are:
Do you think I am on the right track?
Is it most likely to be a video codec rather than audio codec causing the problem?
Does anyone have any great suggestions on solving this? (I suspect the problem would continue even with a reinstall of XP, and of course rolling back the current codecs would mean I couldn't play my newer MPG files).
Thanks in advance for any suggestions.

[ammck55]

I don't know if this will help, but here's an old link to a Disappearing Codecs in XP (http://forum.doom9.org/showthread.php?s=&threadid=24305) thread. Once in awhile, it still comes in handy.

ammck55

[johnt]

Thanks for that, but it checked out clean on my PC.

Many of the MPG files on my machine use the Elecard MPEG2 Demultiplexer, Ligos MPEG Audio decoder and MPEG Video decoder (according to File Information in Winamp).

Yet some MPG files - invariably the 'older' ones - have this problem while 'newer' MPG files using the same decoders don't. Is this weird or what?