MS-DOS 5 Upgrade Rap
This is about as cheesy as it gets. While MS-DOS 5.0 is not necessarily a radical step up from previous incarnations kernel-wise (and some of the features were adapted from MS-DOS 4.x), it does include a number of external components for handling additional memory and the like. The inclusion of these components was critical for taking advantage of the beefier hardware capabilities of the 386 and 486 platforms, which were starting to grow in popularity. As such, Microsoft emphasized the importance of upgrading the only way they knew how to: create a rap music video for software retailers.
By the looks of it, this was originally digitized by NJRoadfan on YouTube.