Right. Just tried a few things.
@Trooper
I can't find an earlier version of Opera to download, so I can't try 6.05 :-(
@ShadesOfGrey
The link and suggestion you supplied didn't work either :-(
@levelLORD
I installed Java with Netscape 7.0, then again with Opera. I removed Java and Opera, and reinstalled them. They still don't work. :-(
Preferences ---> multimedia, everything's fine there, all on what you've said. That was the first thing I checked before posting here.
Don't worry, I won't be using IE6! ;-) I'll use Netscape as a backup, failing that, I'll install K-Meleon aswell :-)