Help with EFS

Hello
(Apologies for crosspost, I do not know where to post it. Searched
something similar without result.)

I'm new to EFS.

I would understand how to use it and to expect from it. I have read many
sites and many theory but not much I have found in practice.

I have done the following things.

I have crypted some files using the property tab of a directory.

After, I have exported the private key in a separate file. I have set
the flag delete if successful export, and it told me something like "you
can not anymore delete or decrypt..."
I am confused now, because I CAN STILL open and do everything with these
files. So, what is the point of exporting and deleting the key???

Maybe it has still it somewhere, I thought...

So, I went in the same snap in console and I deleted under certificates-
personal the entry with my account name, and under reliable accounts I
did same thing.

After this, I CAN STILL open and do everything with these encrypted files.

So, I changed the admin password and (obviously)... after this, I CAN
STILL open and do everything with these encrypted files!

I do not understand what to do to render unusable these files without
the little key file I have removed from PC (everyone says put in floppy
- no floppy from years ago here - and keep safe, ok but what is this? if
i still access the files)

If someone steal the hard disk and reset the admin password with some
utilities, he can still read these files? EFS work only if the disk is
put in another PC as slave?

Please help or address to a pratical tutorial...
Thx