Machine: Inspiron 9400 w/Windows Media 2005

It goes without saying that you've tried to remove it using the uninstallation tool first, also in Safe Mode. In fact, I've only managed to uninstall McAfee adware in safemode.
This only applies to an IE error I had (or whatever errors you have) that stopped me from running the uninstallation. I didn't want to manually edit the register either that McAfee suggest.

This is a way to do it without all that.

The uninstall program to the trial version resides in c:\PROGRA~1\mcafee.com\shared\mcappins.exe
and as you guessed, you can pass parameters to it, allowing you to remove McAfee in a few steps.

Path and general parameters:
c:\PROGRA~1\mcafee.com\shared\mcappins.exe /v=3 /uninstall=1 /interact=1 /script_proactive=0

Individual parameters:
Firewall: /appid=mpf /start=C:\PROGRA~\mcafee.com\agent\uninst\mpfrem.ui::uninstall.htm
SecurityCenter: /appid=msc /start=C:\PROGRA~\mcafee.com\agent\uninst\screm.ui::uninstall.htm
SpamKiller: /appid=MSK /start=C:\PROGRA~\mcafee.com\agent\uninst\mskremui.dll::uninstall.htm
Uninstaller: /start=C:\PROGRA~\mcafee.com\agent\uninst\comrem.dll::uninstall.htm
VirusScan: /appid=vso /start=C:\PROGRA~\mcafee.com\agent\uninst\vsoremui.dll::uninstall.htm


For a full story and details see:
http://www.sigg3.net/entry/990

Thanks!