Big purple bar across my screen!

[Xalioniaf]

Basically, I was messing around with Windows Movie Maker, and out of nowhere this big purple bar appears over the audio bar (the one that takes the audio from the movie). I think nothing of it, but when I switch to firefox to surf the net while my movie is saving, the purple bar didn't disappear. In fact, it's sitting there right now...scheming...plotting...
Why is it there? D:

Edit: Aaaand I turn around, turn back, and it's gone. Picture to show I'm not insane though.

 

[Chuash]

lag in your computer?

I mean.. you switched back to firefox while you were in the process of saving your movie.. right?

there you go. I hope that helped