Dealing with Download you can always download the mouses application and if you dont have the cd you can flip the mouse upside down and locate the maker either logitech, microsoft etc and then from there you need to goto that manufacturer website such as logitech.com if that is yours and then you will have to locate SUPPORT and DRIVERS/SOFTWARE there should be an input for the specific Model that you have and once you locate it I would suggest you download and install that software. I would also suggest that you should try different batteries in your wireless mouse, You can also make sure that you are pressing the connect button on both the USB transmitter and underneath the mouse also press the "CONNECT" button. if all else fails you might have a bad Mouse and if its the wireless usb transmitter or the actual mouse laser then unfortunately last choice would be to go buy one I know www.bestbuy.com
sells them starting at $15. Good luck and please rate me if I have helped you with your solution. Thank you and have a nice day.