Can't upload or down load McAfee updates

Tried to download McAfee update from the 'net and it didn't work.  In the meantime I'm getting messages that pokapoka79.exe is having problems and that Winfixer is trying to run.  Was able to get onto the 'net long enough to find out that winfixer is a virus & pokapoka is adware.  Deleted winfixer but pokapoke won't be deleted- says it's read-only or is already running.  Tried to reload McAfee from the security restore disk but can't do it.  Can't load anything- up or down.  Do viruses prevent this and did just trying to delete winfixer like any other file not do the job?  I'm not getting any messages about it anymore but computer is unusable so something is up.  Tried defragging & got rid of all music files & deleted AIM & downloaded games which freed up space, but still not helping.  Wasted a whole day on this yesterday.  System is constantly freezing up.  Help!