Some older DJ controllers and external sound cards only have 32-bit drivers. To interface with this hardware, your software must match the architecture.
If you are running a 32-bit version of Windows 10 or 8.1, the 64-bit version of VirtualDJ simply will not launch. How to Download VirtualDJ 32-bit Safely
Double-click the .msi or .exe file you downloaded.
Go to Settings > Audio and adjust the "Latency" (Buffer size). If you hear crackling, increase the buffer; if there is a delay when you touch the jog wheel, decrease it.