Windows 7 - winload.exe has no digital signature, can't boot even to F8

I recently installed another Windows to my computer.
It works and boot, but the older Windows can't boot and gives an error of

"\Windows\System32\winload.exe" cannot be trusted because of its digital signature.

It tells me to go to F8, but when I press F8, it goes back to error screen of winload.exe.

I tried start up repair options with both disks (I have two disks in the computer), but start up repair was just messing up the boot. After several times of repairs, I came back to the boot screen, can boot to the new.

Is there any way that I can solve this?

Thanks.

Run System Sweeper.


PUT SYSTEM SWEEPER ON A USB STICK


System Sweeper, https://connect.microsoft.com/systemsweeper, allows you to start an infected PC and perform an offline scan to identify and remove viruses, rootkits and other advanced malware. System Sweeper is a free standalone, bootable malware and virus remover from Microsoft.

Safety Scanner, Microsoft Safety Scanner - Remove Spyware, Malware, Viruses Free, is free, downloadable, provides on-demand scanning and helps remove viruses, spyware, and other malicious software. It works with your existing antivirus software.

If the target computer has a working internet connection, then you may prefer to use the Safety Scanner.


Download System Sweeper (about 576 kB):
https://connect.microsoft.com/systemsweeper

Insert 256 MB or larger USB stick into a usb port.

Run the downloaded program--mssstool64.exe or mssstool32.exe

Choose the option to install to USB.
Caution: The install program will format the usb stick.

The install program will download about 200 mB more.

After the install is finished, leave the stick in the usb slot.

Run the program you downloaded once again.

This 2nd run, and any subsequent runs, will download the very latest anti-virus definitions (about 60 mB).

To keep System Sweeper up-to-date, simply reinsert the usb stick and run the installation program again.

The initial, full scan by System Sweeper can easily take a couple of hours, but subsequent quick scans will take only a few minutes.

Remember, your computer is being very thoroughly checked for all types of malware.

The results of System Sweeper will be in:
\Windows\Standalone System Sweeper\Support as a file with a LOG extension. You can view this file with Notepad.

Thanks, I will do that right now.
I was doing weekly scans and this happened right after the new Windows install.
I can still reach the files from the new Windows.
Is there any way to directly clean winload.exe if it is infected?

System Sweeper will take care of any infected files.

Ok, I was just reading about it. I didn't know that it was a bootable option.
Thanks.

UPDATE: While the program was preparing the USB, I found a winload~1.exe in \Windows\System32.
I gave the ownership of winload.exe to administrators (of new Windows) from trusted installer.
I changed its name to winloadd.exe.
I changed the name of winload~1.exe to winload.exe, and now I am able to boot.

I thanks you for the program suggestion, because it seems a very good option to clean an operating system with bootable media.