Continue without verification?

[cravuhaw2C]

Under Microsoft Windows 7 OS, I "burned" install55.iso to a CD which I then inserted into a CDROM slot and rebooted my laptop computer.

When the installation process reached the stage where I had to select some sets, I selected only the ones that I needed.

I was stuck at the next step. I was asked the following:

Directory does not contain SHA256.sig. Continue without verification?

What should I do? Can I copy SHA256 and SHA256.sig to a USB flash drive and issue a command to the installation routine, telling it that the required *.sig file is on the USB stick?

Note: I had downloaded both SHA256 and SHA256.sig a few days ago. As the signing key of install55.iso, in the form of *.asc file, is unavailable, there was no way for me to verify the integrity of install55.iso using gpg4win under Microsoft Windows 7.