I am told when I startup that 'some components of Active Shield are missing' and am therefore not protected. I removed and restored Mcafee. everything fine for a couple of days but now its started again with thesame message,. Any ideas?

your computer probably has a trojan horse or some type of virus that isn't letting it install the active shield components. I would go and install a free anti-virus like AVG or Anti Vir and uninstall McAfee because it sucks.

If he's infected with a trojan that's affecting the on access scanner installing a different scanner is unlikely to help.

Try using Trend Micros Sysclean + Virus Pattern to clean your PC.

More cleaning options and tools are in RescueME see my sig.

Also run/install adaware and spybot.

If your still having problems post a HijackThis Log in this section of the forum

McAfee support forums if you think it's just a McAfee problem try this forum.