Welcome
In the case of Malware the correct answer depends on many factors. If it is a serious infection such as a root kit, reinstall is the only answer.
If its minor, tracking cookies, etc. If you are sure of the date that the infection was on the machine, you can indeed go back with a system restore to a date before that point.
Now, I based my answer on known facts, as other posters may, too, but its subjective and you may get responses that indicate you should reinstall.
For other problems with the OS, I would suggest a System Restore. YOu should keep them updated, weekly, and also update after every change to the Operating System
A sytem restore take a picture of your Operating System, if you go back in time, that picture is used. If there is a bug it is gone. If the bug is not in the Operating System the problem will remain and you will be forced to take other action, the last being a reinstall.
You can use SFC
Repair Install etc.
