On just about all systems you can have any combination of drivers including: Chipset, IDE controller, SCSI controller, AGP Controller, IDE Filter, AGP Filter, RAID Controller, Firewire Controller, USB 1.1 and 2 controllers, monitor drivers, display card drivers, Glide/OpenGL drivers, ACPI/other power management drivers, sound card drivers, temperature controller drivers, NIC card drivers (Ethernet, Thin/Thicknet, Wifi, whatever), PDA drivers, printer drivers, PCI Controller drivers, and so on.
Most of these are installed by WIndows, but Windows drivers often have the most basic support and almost always are out of date, especially video, sound, and NIC drivers.