windows media player or realplayer wont work so what should i use?

"Won't work" means what?

Most likely you are missing some codecs or you have broken your codec system.

A standalone player using its own codecs may work - try VLC media player.

AVI works in Media player

You either do not have them enabled for media player or you need to install codecs for the avi to run.

DIVX player plays avi and so does quicktime

Download K-Lite Mega Codec Pack from here and install. While installing, you'll come up on a screen with loadsa check boxes and stuff. Check all the boxes u see except for the Morgan Mixer or whatever it's called. Then let it install and u will be able to play any AVI file in Windows Media Player.

If you are still having issue then uninstall ALL your codecs because you most likely also have a codec conflict issue as well. Then install CCCP once. Thats the the Complete Community Codec Pack which has it all ....

VLC was my fave player until it went ms on me when it came to mkv files.

......
ms - microsoft - as in lockups, nonsensical error messages and various colours of the rainbow screens of death

What do you mean by this? I still use VLC to play my mkv files.

I use K Lite Mega Codec Pack together with Media Player Classic and I can read every single video...
Quicktime, Real, flv, avi, wmv, and all the other formats...
It's a really great codec pack and Meida Player Classic is really low on ressources...
Regards