Choppy while playing in Virtual DJ but not on the screen is indicative of something running in the background on the computer, not DJ related. While the list of cause possibilities is endless, I would start with my anti-virus program and tell it not to scan mp3, mp4, or whatever other media-type files you play. The quickest and easiest step to see if it might be your culprit is to temporarily disabled any anti-virus, malware, spyware programs and check out if the stuttering is gone (which my guess is, it will.) then fine tune to raggy program in its options.
Other common possibilities include programs trying to auto update themselves, superfluous bloatware running in the back ground, and other software related happenstances.
Good luck, better skill.
One other thought popped into my head. Have you done a full scan of your entire collection of media files? If VDJ is updating a specific file for bpm, volume, and all its other database structures while a track is playing, it almost always does a number on the VDJ computer screen but rarely if ever does so on the output screen.