Download and save HC to your computer. Then, right click on the exe file and choose "run as administrator. That's it.... if you already have the software on your computer then simply right click on the desktop icon and choose "run as administrator."
Try it first without removing anything. Most people do not have to remove previous downloads. If you have a problem then go to your Add and Remove Programs and remove the conference software. After you do this then go to your Program Files and delete a folder called "Conference".