Your canon should have come with a software disk, if so make sure you have installed all the software, then you can update it or download it if you did not get the disk by following this link:
http://www.usa.canon.com/consumer/controller?act=ModelInfoAct&tabact=SupportDetailTabAct&fcategoryid=226&modelid=11933#DownloadDetailAct
Try that link, it should take you to the drivers and downloads for the 5D, if not go to this link http://www.canon.com/cusa/index.html and you will need to hover over 'support' and click on 'consumer' then select your product and then select 'drivers and downloads'