Windows7 constant updates

[#1]

I am running Windows7. Every third day, when I start the computer, I get a Microsoft Update pop-up saying that there is "One important update" to install. So I install it. Then, three days later, the same thing happens. The updates are of different numbers, different sizes, and some require a reboot.
As a test, sometimes I haven't installed it, but ignored it for a week or more. After that time, it still says that there is one important update to install!
My wife does not get this constant updating on her laptop, it's just on my desktop.
Does anyone else get this? It's been going on for about two-three months now and I'm beginning to wonder if it is a genuine Microsoft update.
Any advice will be very gratefully received.
Many thanks.
Keith

[#2]

You should be able to look up the number of a Microsoft Update to find out what it is for; that would give you clues as to what is going on.  Microsoft Security Essentials, if you use it, requires frequent updates but these are usually 'silent'.     

[#3]

you could always try Turn Auto update OFF and just manual update 

[#4]

As above - it may well just be a Windows Defender / MSE virus definition update.
Mine update every couple of days on my Win8 machine.

[#5]

Thanks for your replies.
I have had this computer for four and a half years. Until recently, I rarely got any updates apart from the monthly batch.
It was starting to get them every couple of days which made me wonder if they were genuine.
Most of them are:
Definition Update for Windows Defender, or  Security Update for Windows.
So all seems to be OK .
I've always set Windows Updates to notify me before updating, rather than doing it 'Behind my back'
Thanks again,
Keith

[#6]

If you launch Windows Update and view update history you can see the sequence of updates and check they all succeeded.  In my case, although Windows Defender is suppressed from scanning by my regular security software, it updates itself every three or four days.