I received a phone call from someone claiming to be from Microsoft/Dell/HP etc, and saying that my PC is infected and they need to access it to take care of it. Is this legit?
No. Microsoft and similar companies will not call you unsolicited. They will only call you if you reached out to them first.
I was browsing the web and a message came up saying that my computer is infected and I need to dial an 800/866/877 number in order for someone to clean/unlock my pc. Is this legit?
No. That is a pop-up that is meant to scare people. The end result of you calling that number can be actually getting an infection or them locking you completely out of your pc. This doesn't mean that your PC doesn't have any adware or malware redirecting your links, We just want to let you know to not call that number. Close the web browser you received the link in, or reboot your machine.
When I turn off my PC I hold down the power button or flip the switch in the back. Is that ok?
Absolutely not. That would be the equivalent of turning your car off while doing 60 on the highway. Cutting power to the PC while it is still in Windows can cause issues with your operating system, even to the point of the machine not booting correctly. That "hard reset" is reserved for serious issues preventing normal shutdown.
My PC upgraded to Windows 10. How do I go back to what I had?
If it is within the first 30 days you can go back. Any longer and it is not possible without reloading your PC.
Click on the Notifications button
Select Update & Security
Click Go Back to Windows 7, 8, 8.1 (Whatever version you had will appear here, not all 3)
WHen it asks for a reason, you can choose whatever you want
Follow the prompts to begin the reversion. You can choose to skip the check for updates portion, this speeds up the process.