How to unencrypt?

[Janie]

I have files on one drive that were encrypted. I have a certificate that
might be the one I need.
How is it exactly I go about opening the file or files using the
certificate?
I can t seem to find the answer to that simple question.

 

[Dusko Savatovic]

You need to install certificate in your personal store. This is normaly done
by double clicking on a certificate file with .pfx extension. If it's the
right certificate, you will open the file sucessfuly.

If it is a recovery agent's certificate, from the security point of view you
should not install this certificate to your personal account (you would then
obtain access to all encrypted files). Instead, you should create a new
account, log with this account and install certificate. After you are
finished with recovering data, you should destroy this account and it's
profile. This should usually be done by at least two persons.

You can use certificates mmc to watch, export and import cerificates:
Start/Run
mmc
File, Add/Remove Snap-in
Certificates
My User Account

Expand Personal/Certificates.
Your certificates are here.