There are so many nasty worms etc., out there, I have almost given up, except for one piece of software.
Go Back 3.0 is fantastic. I have been running some version of Go Back for years, and it has saved me more times than I can remember. If you have a problem, screwed up a new software install, or what ever, you just click on GoBack, and you will see times, and dates listed. you click on that time/date, and the computer will go back to that time/date. You will lose everything on your computer from that time forward, including the nasty stuff.
One note, be sure to find version 3.0, because the new 4.0 is not good at all, and has caused a lot of problems. 3.0, if you can find it, sells for about $30.00 and is so worth it.
PS: Microsoft licenses a version of GoBack, and they call it System Restore, but no where near as good as GoBack 3.0