My usb ports not working but device manager says they are fine

HI I’m not very computer savvy but really need some help. My usb ports on the back of my computer don’t seem to be working even though the device manager says that there is no problem with them. The PC is about 5-6yrs old and is running windows XP. The USB keyboard, mouse and printer work fine on my mac but not on my PC. Someone has told me I need to add new usb ports to the computer. I’ve seen these on sale on ebay but I don’t know which type to buy. Can anyone please help as I have work on there that I need to hand in for my finals.Thanks.