Did you run the MCPR removal tool when you uninstalled? MCPR is found at the top of this page under Useful Links.
This document form McAfee will assist you installing and activating your software.http://service.mcafee.com/FAQDocument.aspx?lc=1033&id=TS100119
Please be sure to follow the directions and run the mcAfee Preinstall tool found within the link.
Let us know if this works for you and good luck
apparently it worked, i hope it keeps on working properly now... thanks