Brookstone wireless mouse
Connect your wireless mouse while your wired one is in the computer. Now, if there were any CDs that came with your mouse then put them in your CD reader and go through the installation process. If there were no CDs, then search online and find a driver the suits your mouse. Download it and install it.
Do not unplug your old mouse while installing the new one. You need something to use while you can't use the new one :P