Card Swiper / Data Reader

I have a magnetic card reader which we use to update health card info in our office. We purchased new computers but are using the same Windows XP Pro software. The card reader is connected to the PS/2 keyboard slot as we now have a usb keyboard. The green light is on but I get no reaction from the reader what so ever. CAn you tell me if there is a place within windows where I have to tell it to recognize the card reader?