MJ:
System Restore is under Programs, Accessories, System Tools.
It allows you to restore your system to a previous working stage.
It will undo all changes in your PC from that day on.
Depending on where your data is located, it may be remain untouched or not.
Backup your important data and later on do the system restore.
Your PC will look exactly as it was the day you have chosen to restore.
If you are not familiar with system restore operation, get help from a friend.
Carlos