Plug and Play hardware will automatically be detected by the OS upon startup. Add/remove hardware in the Control Panel is for installing devices that are not Plug and Play.

Don't forget that some of these devices will have to be configured for IRQ, DMA and/or I/O addresses using jumpers beforehand, so make sure you have a note of the free resources.

An OS with IRQ steering, such as Windows 98 SE for instance, can have many devices sharing IRQs, but a device that is not Plug and Play, you will not be allowed to use an IRQ that has already been taken.