To answer your original question:
In general, if Windows doesn't recognize a device, it simply won't install drivers for it. This won't generally cause crashes. The device just won't work. But it's a major issue if the device is the disk controller. The system can't read the disks. Windows will stop to prevent system damage.
Many devices have alternative, generic, functions. Like all video cards can work in generic VGA mode and IDE controllers can work in generic IDE mode. If Windows recognizes what the device is, but doesn't have specific drivers for the device, Windows will install the generic drivers. The device will function, but likely with fewer features or more slowly than with the device-specific drivers.