You can run System Restore on your computer by following below steps:

Start button
In Search box, type System Restore
Click System Restore
Follow the steps in the wizard to choose a restore point and restore your computer

This will restore your PC to earlier state.

There are various types of antivirus softwares available such as:
1) AVG
2) Avast
3) Avira
4) Quick Heal
5) Noton

Antivirus programs are designed to provide protection for your computer from malicious software’s. Here is the list of functions performed by the antivirus software’s:-

1) Real-time protection
2) Threat detection
3) Automatic updates
4) Alerts
5) Additional functions depending on the antivirus software, such as e-mail protection, instant messaging protection, identity theft protection and pop-up blocking.