Embedding MPEG1

Hi. Can anyone help me with this? I'm going a bit crazy...

I had embedded some mpeg-1 video into my webpages, and everything was fine.
Then I had to clean and reinstall everything on my hard-drive: OS (WinXP) and
all software. Fortunately, all my work was backed up. But now, the videos I had
previously embedded do not load in the page (no TV screen). I tested some WMV
files, and they load ok, but not the MPEGs. I didn't know if this is because I
previously had installed DivX and Xvid. I would try to reinstall these, but I
don't want to go installing stuff as an experiment. Any ideas would be a big
help. Thanks.

Donny
PS: I'm a bit of a novice, so super-techno help may go over my head. Thanks
again.