Is there a legal way to remove DRM?

I paid for and downloaded some videos a long time ago that apparently came encoded with DRM. However, I moved these files onto a new computer and external hard drive, and now when I play them it asks me for a username and pword, which I don't have. Is there a way to either (a) find out my username/pword so that the files work? or (b) legally remove the DRM encoding so that I can not only play my paid-for files on this computer, but anywhere I take my files?