Can't get a connection to the mouse, keyboard

Hello,

i am having an issue with getting a connection from the tower to the mouse], keyboard and wireless modem. the tower turns on, the fan runs really fast but there is no connection to the keyboard, mouse or modem. i have turned it off unhooked everything and hooked it back up. still nothing. i opened up the tower and blew out the dust. again the same issue. what else can i do to get a connection?

thanks
lisa nelson