Hi Sidenia,
Please follow the below steps to get rid of the error.
1. Set your BIOS so that it uses the DVD drive as its primary boot device.
2. Boot the machine with your Windows 7 Repair CD or with your Windows 7 installation DVD.
3. Press a key if prompted to boot from the DVD.
4. Select "Safe Mode Command Prompt" when prompted.
5. Log on as Administrator if prompted.
6. Select Repair when prompted.
7. Select System Restore when prompted.
8. Set Windows back to a point before this problem occurred.
Regards,
Lokesh