I suspect the real problem here is your keyboard, not WMP. You might try uninstalling the Logitech software and driver associated with your keyboard and then reinstall it.
Another troubleshooting step would be to try another keyboard. Do you have an old standard keyboard lying around? Try it.
If the problem is, indeed, a keyboard issue, then you did not need to uninstall IE7 and I suggest you reinstall it. Or, get the Firefox browser and use it. Either way, I would not continue with IE6.