Windows 7 adds a great new security feature called UAC. There are certain situations where you have to disable UAC which you can do by following the below steps.
1. Open control panel by going to the start menu -> Control Panel
2. From the control panel select User Accounts And Family Safety
3. Select User Accounts
4. Select Change User Account Control Settings
5. Move slider bar to the bottom so it is at never notify. Then click OK.