Steps:
1. Open "My Computer" or click the Yellow Folder icon in the taskbar.
2. Click the location bar and type "%appdata%".
3. Navigate through you .minecraft folder until you see "minecraft.jar"
C:\Users\********\AppData\Roaming\.minecraft\bin
4. Right click the "minecraft.jar" file and click previous versions.
5. You may or may not have previous versions depending on if you even have any system restore backups.
6. Click the one the fits your needs and restore!
