EFS crypted filesystem

long time ago i turned on the efs encryption on my secondary hdd
now i had a systemcrash and basically lost my main hdd. I reinstalled the complete windows, and no i cannot access any file on the secondary HDD cause everything is crypted and i don't have the certificate.
BUT i have one file on my USB Pendrive being not crypted. The same file is also laying in the Secondary HDD.
How can i use this uncrypted file to decrypt all those encrypted files?

This is why idiots shouldn't use computers.

Nonetheless i'll try to help. What software did you use to encrypt the second hard drive? and what did you use to decrypt it? A keyfile, a password, your windows account, your private key or a combination? If it's what i think you mean and you used PGP/GPG and you don't have the certificate. I strongly suggest you run some recovery software on your main drive like TestDisk or PhotoRec to get that cert back.

To answer your last question, you can't. There might be other ways to save that data.