McAfee Firewall Won't Stay On; Can't Turn on Windows 7 Firewall; Computer Keeps Restarting; and I can't access a file because my computer says I don't have permission

Uninstall McAfee completely.

Do not use any product that claims to make your computer run better.  Virtually all of them are either bogus, themselves an infection, or put your computer at risk. Remove everything that claims to be there to prevent infections or claims to make your computer run better, with the singular exception of just one antivirus product.

This is a controversial topic, but your choice of AV software may be something you want to take a 2nd look at.  I suggest you visit this web site to get a sense of which AV software does the best job, depending on what kind of user you are:   http://www.av-comparatives.org/   This is a non-profit that has been around for a long time and I trust their results.

When you interpret these results, keep in mind the difference between a product that detects 95% and another 99% of infections, is actually 5 times more likely to allow an infection.

I look after about 150 Windows PCs and have for over 13 years.  Up until last September, the only AV software I would allow my clients to use was Norton Antivirus.  Please note well that that is not the same as any other Norton product such as 360 or Internet Security.  My clients have rarely ever experienced infections.

Last September Symantec (owner of Norton) decided to no longer sell such a product.  After a lot of research, I decided on Bitdefender Antivirus 2015+.  I have installed it on most of those PCs so far and there has never been a problem, and this has been over a course of about 11 months now..  It is a better product than Norton.  It is also not expensive. One of the things I like most about it, is it silence and unobtrusiveness.  Especially if you silence its "Wallet" function. 

My clients know well that if they install any "Internet Security" product, I will not work on their computers until it is removed.  I learned very well the hard way that the other components in these IS products (other than the AV itself) cause more problems than any benefit they bring and mostly work by shutting down the Windows component that does a very good job of that particular task anyway.  The problem was that when I started to work on a computer with an IS on it, I could spend hours trying to diagnose the problem, only to discover that by removing the IS product, the problems became much clearer and easier to solve.  I think the IS product is actually hiding the problem.

Like I said, this is a controversial topic and you will find a lot of very strong different opinions.  I just know that mine is based on a pretty large sample over a long period, and these are typical consumer Windows consumers.

Note well.  You should never have more than one protection software installed.  Always ensure that you completely remove any and all protection software packages before installing a new one.  That includes software that may have come pre-installed on your computer when new

You cannot fully remove most any AV software by simply using the standard Windows 7 uninstall tool.  Most of the majors also publish a "removal tool" that gets the rest of it.  If you do not completely remove it, it will cause very hard to understand and diagnose problems.