You can verify your McAfee installation by running the McAfee Virtual Technician http://mvt.mcafee,com/ and to check the version numbers open SecurityCenter by double-clicking the taskbar icon and then selecting 'About" (older versions from some 3rd party suppliers you have to click Navigation and then About).
McAfee may be having trouble getting past disk read errors.
Go to Start/Start Search and type cmd
Right-click cmd and select Run as Administrator
Type in chkdsk /r (with the space) and click Enter
It will say it can't continue because the volume is in use, try at restart Y/N?
Type Y and click the Enter key. Reboot and let it do its thing.
If you have more than one drive letter - i.e. several partitions and the system you are using isn't C: then type chkdsk X: /r (spaces included and alter X to whatever).
Another block is often when there are ovely compressed files, i.e. compressed files within compressed files. It sometimes takes forever to unpack them. A compressed hard drive can also be a slow down.