Follow the steps given below should help solve the problem with a corrupt Master Boot Loader (black screen with blinking cursor) issue.
First, make sure you have your Windows 7 CD or a Repair CD handy.
Step 1: Change the boot priority to CD ROM in your computer BIOS.
Step 2: Insert your Windows 7 CD ROM and press any key to boot from CD.
Step 3: Click on “Repair your computer”.
Step 4: Select the correct installed Operating System and click Next.
Step 5: Choose Command Prompt from the list of recovery tools.
Step 6: Type “diskpart” and press Enter.
Step 7: Type “select disk 0 (zero)” and press Enter.
Step 8: Type “list volume” and press Enter.
Step 9: Make a note of the drive letter which indicates the type of volume as “CD ROM”.
Step 10: Exit the diskpart by typing “exit” and pressing Enter.
Step 11: Type the letter of the drive. For example, if the drive letter is F, then type “F:” and press Enter.
Step 12: Next, type “cd boot” and press Enter.
Step 13: Now type “dir” and press Enter.
Step 14: Now you are left to restore the boot sector code. Type “bootsect /nt60 SYS /mbr” and press Enter. There are spaces in this code, so make sure you enter them too.
Step 15: You will see a message that says “Successfully updated disk bootcode”. Now type “exit” and press Enter.
Step 16: Now select Restart.
Congrats, you have successfully restored Master Boot Record with your Windows 7 disk.
Do let me know if you encounter any problems during the process.
Dragon Blogger Notes:
If you don’t have access to your Windows 7 media, and you have a friend’s PC or another PC you can build a Windows PE Rescue Media with Macrium Reflect which is free. If you follow this article about cloning Windows SSD Drive you will find instructions on how to use Windows PE Rescue Media to restore your Master Boot Record or fix mbr issues as well, these instructions should work for any Windows OS install disk as a backup. As noted, since you will need to have the Windows PE Rescue media ahead of time, or have to build a USB or CD image of it from another PC it would be easier if you have your original Windows 7 media disk and follow the above instructions.