Hi, Peruka! First of all, welcome to MobileRead!
DRM is a way the ebook publishers have of telling us what we may do with the ebooks we purchase and what devices we may read them on. It's a very hot topic, both here and elsewhere online. Calibre will only catalog and move DRM'd material, it cannot open or convert any DRM'd files. Amazon has a Kindle application you can download for free that will let you read your Kindle DRM'd books on your laptop--it will download them for you without any conversion needed. Ithink it will even sync with your Kindle so you can pick up where you left off reading on your Kindle to read on your PC.
DRM removal is a topic that is of questionable legality, depending on where you live, and as such instructions are not discussed here. However, if you Google terms like DRM removal and Apprentice Alf, you will find lots of interesting and informative information.