Windows 10 for Dummies
The BEST book for new Windows 10 users. Read one chapter and you will be up to speed when moving from Windows 7 or 8 to Windows 10. Buy from Amazon.
Here is a great utility for Windows 8 & 10. It gets rid of all the scary stuff you have heard about: no more tiles, a new start menu, no more lock screen, etc. These are all customizable. I automatically install this on every new Windows 8 installation and many Windows 10 installations. Never a problem. And it's FREE!
When your computer is acting screwy, download the free version of Malwarebytes. This program will look for all kinds of things that your regular anti-virus software can miss. The paid version of the software will be installed for a 14-day trial. Just let the trial expire and the free version will serve you well.
More memory is always useful, and it is relatively easy to install yourself. I always order memory from crucial.com. Their prices are competitive and they have a utility that scans your computer and tells you exactly how much and what type of memory you can add. Go to Crucial and click on the tab about 1/3 down the page that says "System Scanner."
HDMI cables are necessary for modern home entertainment systems. Your local retailer may want $20 - $50 for these cables. Amazon's cables work just as well for a fraction of the price.