Should i get a new laptop?

You can use your present modem and router to use wifi with your lap top without using your desktop computer. Only for configuration purposes, if and when it is required, you can connect the modem with an ethernet cable to the ethernet port of your lap top. Once configuration is over, disconnect the cable from both the modem and lap top. Now connect the router to the modem and you are ready to use you wifi. I ume you have already configured your modem and router. DHCP should be enabled in the modem. DHCP should not be enabled in the router.