• Remove the ePO agent: http://forums.mcafeehelp.com/viewtopic.php?t=31157
• How to uninstall or reinstall supported McAfee consumer products using the McAfee Consumer Products Removal tool (MCPR.exe)

Internet Security Suite

• When trying to register, make sure you are connected to the Internet, and that you've set the proxy in IE if required. Otherwise you may get stuck on a blank / white screen, which seems to have frozen.
• SystemGuard protection is disabled - try setting SystemGuard service to automatic, and recovery options to always restart the service. Also try this fix from McAfee to give Builtin\Users read and write permission to the MClOGS folder. (more info in this McAfee forum thread)

Total Protection Service

• Manually install Total Protection Service