mfeavfk01.sys and mfeavfk.sys are system files belonging to McAfee so why would you stop it? The 01 simply means the original is being replaced for some reason. This can happen if you are in the habit of using registry cleaners and/or optimizers, which can wreck software installations in a flash. Is there something suspicious happening on top of that? Also what is this 'different antivirus program' you mention?
What is your operating system and service pack? Also please open McAfee SecurityCenter and click 'About' and post the version of SeucrityCenter.
Your installation may benefit from ruinning the Virtual Technician as it often repairs minor problems: http://mvt.mcafee.com/
If you do not have McAfee installed then uninstall any McAfee component that still appears on Control Panel > Programs > Uninstall a Program, (Add or Remove Programsd in XP)
then run the MCPR cleanup tool listed under Useful Links at the top of this page.
Note: never install 2 antivirus programs at the same time as they will surely clash and actually could leave you open to infection.
Moved provisionally from Community Help to SecurityCenter as a more appropriate spot.