WHICH annoying picture?
Has your WMP loaded the appropriate album art?
Or is it one of WMP's "visualizations"?
WMP will "fill in" some missing data in the music library displays
you can turn those displays off by clicking in the bar where track title, artist, release date, etc are displayed and checking or unchecking them.
generally speaking wmp displays the meta data and while things can be edited (accidentially or otherwise) within WMP this doesn't change the metadata, only the displayed date in WMP.
As for a tag editor for editing your metadata:
It's what I (and many others here) use. it is the best tag editor I've ever seen and it's FREE! you can't beat that combination...
For converting to and from different audio file types I'd suggest that
you download "Switch sound" file converter from NCH software.
This is a full featured trial version that drops back to a limited free version in 10-ish days, but so far I can't find anything I want it to do that the free version doesn't do.
And there are only a few "please buy me" messages tha pop up, one before the trial expires, one after the trial expires and another a few weeks later ("You've been using this a while you wanna buy it yet?") And after that nothing...
it will not convert "protected" WMA's