You most likely need to obtain and install drivers for all your hardware.
You will need ones specific for Windows 98.
Did your PC come with any CD's with drivers on them?
If you have a brand name pc, you can go to the manufacturer's website and there should be an area there for their customers to download drivers. Just enter your pc's serial number and you will be offered the drivers to download.
Or you can search Google with the brand & model number for each item of hardware that isn't functioning properly, followed by the word 'drivers'. You might have to actually physically look at the hardware to find out what it is, if you don't have it written down somewhere.