My screen is blank and says manager cannot reboot

Uninstall the OS and reinstall.

Screen on what? Why can't people put enough info to answer a question? Are you talking about Windows, and the Windows "boot manager"?

here are some fixes to try:
(located here: https://neosmart.net/wiki/bootmgr-is-missing/) I recommend working from bottom up, and trying system restore...unless you have a boot CD/DVD ...in which case try startup repair first.
<Donna> https://everythingit.us
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This repair method works if you have the Windows installation disc.
Here are the steps to fix the BOOTMGR error with an installation CD:

1. Insert your Windows install CD
2. Restart your computer and boot from the CD
3. Press any key when you see the "Press any key to boot from CD or DVD" message
4. Click Repair your computer after selecting your language, time and keyboard method
5. Select the drive of your Windows installation and click Next. The standard drive is usually C:\
6. Select Startup Repair
7. Wait for the process to finish

Fix #3: Use bootrec.exe to rebuild the BCD

bootrec.exe is a tool built in the Windows Recovery Environment (Windows RE) that you can use to troubleshoot and repair the error.
bootrec.exe can repair boot configuration data and master boot records. BCD, which stands for Boot Configuration Data, contains boot configurations options and controls how Windows is started.
Here are the steps for accessing bootrec.exe to rebuild the master boot sector:

1. Insert your Windows 7 or Vista install disc
2. Restart your computer and boot from the CD
3. Press any key at the "Press any key to boot from CD or DVD" message
4. Choose Repair your computer after you select the language, time and keyboard method
5. Select your Windows installation drive (usually C:\)
6. Click Next
7. Select Command Prompt in the System Recovery Options box
8. Write the following command and press Enter:bootrec /rebuildbcd

Fix #4: Run System Restore

The next solution will work only if you have System Restore enabled on your Windows.
Here are the steps for restoring your PC with System Restore:

1. Insert the Windows 7 or Vista install disc
2. Restart your computer and boot from the install disc
3. Press a key when "Press any key to boot from CD or DVD" message appears on your screen
4. Click on Repair your computer after selecting a language, time and keyboard method
5. Select the drive where you installed Windows (usually C:\)
6. Click Next
7. Select System Restore from the System Recovery Options box
8. Follow the System Restore wizard instructions to select a restore point
9. Restore your PC by clicking Finish

Fix #5: Use bootrec.exe to fix the boot

The partition boot sector is stored on the hard disk drive and contains the necessary code to start the Windows boot process. If this partition is corrupt or not properly configured during a Windows install it would lead to "BOOTMGR is missing or corrupt" errors at startup.
This method needs a copy of your original Windows installation disc.
Here are the steps to fix this error using the bootrec.exe tool, the same tool used in Fix #4 above:

1. Insert the Windows 7 or Vista install disc
2. Restart your computer and boot from the disc
3. Press any key at the "Press any key to boot from CD or DVD" message
4. Choose Repair your computer after you select the language, time and keyboard method
5. Select your Windows installation drive (usually C:\)
6. Click Next
7. Select Command Prompt from the System Recovery Options box
8. Write the following command and hit Enter: bootrec /fixboot
9. Wait for this message to appear: The operation completed successfully.
10. Restart your computer