If WMP6.4 lets you do:
Tools > Options > Performance > Advanced >
then that may help. Or some other disabling of hardware acceleration
Otherwise you could hex edit the mpeg file (easier than it sounds).
For more info, take a look at another post just made to this group
(25May03) entitled something like MPEG Aspect Ratio Problems Explained
and Fixed. It contains more details and some possibly permanent
solutions which may work no matter what video player is being used.
> I had a similar problem, and went searching. I found numerous references
> to WMP "ignoring" aspect ratio settings. But you say it worked previously?
> I had not prior experience of this phenomenom as a newbee. I am using
> DX9 and WMP 6.4. PowerDVD played it properly...