Usb hub not reading external hard drive

Hello,

I just bought a 4 port USB hub as I only have one usb port that works on my computer. When I plug the hub in and the plug my mouse into the hub it works fine but then as soon as I add my hard drives the mouse stops working and it says it can not recognize device plugged into the usb port. My touch pad doesn't work so i need this hub to do anything. My external hard drives work when plugged directly into the computer but will not work when plugged into the hub. Please help!