Hello,
Welcome to Microsoft Community Forum.
This issue may occur due to some third party software/hardware conflict, virus infection or if Boot mgr is missing or corrupted. The Windows boot manager, also known as the boot loader, tells your computer how and which operating systems to load. In some cases, if the boot manager is corrupted you may encounter this kind of issues.
1. What is the make and model of the computer?
2. Do you have Windows 7 installation disk?
- Do you remember making any changes to the system prior to this issue?
To resolve this issue, use the following methods in the order in which they are presented. If method 1 does not resolve your issue, proceed to the next method.
Method 1:
Disconnect all the external devices (printers, scanner, USB (universal serial bus) device and then boot up.
If this corrects the issue then add the devices back one at a time until you discover the piece of hardware causing the issue. Then get updated driver software for the device.
Method 2:
Try booting into Last Known Good Configuration and see if you can boot fine.
Using Last Known Good Configuration
http://Windows.microsoft.com/is-IS/Windows7/Using-Last-Known-Good-Configuration
Method 3:
I would suggest you to re-perform start-up repair using Windows 7 disk.
Startup Repair: frequently asked questions
http://Windows.microsoft.com/en-us/Windows7/Startup-Repair-frequently-asked-questions
What are the system recovery options in Windows 7?
http://Windows.microsoft.com/en-us/Windows7/What-are-the-system-recovery-options-in-Windows-7
Method 4:
If the issue persists, then follow the troubleshooting steps from this Microsoft article and check if it helps:
How to use the Bootrec.exe tool in the Windows Recovery Environment to troubleshoot and repair startup issues in Windows
http://support.microsoft.com/kb/927392
Additional information:
Windows hangs or freezes:
http://support.microsoft.com/kb/2681286/en-us
Hope this information is helpful. Please do let us know if you need further assistance, we’ll be glad to assist you.
Thank you