Originally Posted by Scifibookguy
The important thing to note is that I can also convert the Kindle file in Calibre to, for example, a .mobi, and Calibre processes it just fine. So I think that either Kindle for PC doesn't use any DRM, or Calibre strips it when it imports it.
Out of the box, calibre does not strip DRM, and K4PC does handle DRMed books. Either the books you got from Amazon are free of DRM-infestation (some are), or you are using one of the DRM-stripping tools available (that we can't discuss discuss further on MobileRead).