Important Problem: How To Prevent App From Calling Home?

It depends what level of security you want.

First you'd need to use encryption. Then you could hide the existence of the files, so they are not shown in explorer. Store your data locally, not in the cloud - and never connect to the internet - or not while you are accessing your encrypted notes, which of course you store on external storage which is never connected to your PC when you are on line... and of course you put that encrypted external storage - of which you have at least two copies- in two separate secure locations (!!)

Whatever you use needs to be inaccessible if someone uses a boot disk to access your drive - hence encryption. There are plenty of 'folder hiding' programs, but without encryption, they are potentially insecure.

Now, somewhere amongst that you need to decide:
a. How paranoid are you (that's not a criticism - just a question you need to ask- how much inconvenience are you willing to put up with for the sake of 'absolute' security?)

That determines the means you employ and how arduous and rigorous a procedure you want to follow.

b. Whether you want a free or commercial solution

A practical approach:
Until Truecrypt (free) was thought to be insecure (the arguments for which are somewhat arcane) that would be my recommendation.
Such programs create a container, which is password protected and encrypted.

The user needs to know where the file is, access it with Truecrypt, enter the password.

That file's content then is visible as a new drive letter in explorer- and looks like a normal drive with folders and files.

Maintain backups as usual.

There are newer programs which have replaced Truecrypt - which still works, but is not maintained.

Dalchina, I wasn't expecting such a detailed reply so I'll reply to you soon!

Steve C said:

I only ever store passwords within a password protected Word file on a removeable Bitlocker protected USB stick kept in a secure location. My PC is disconnected from the net when accessing the USB drive.

This seems like a great idea.

EDIT:

Dalchina, I meant to say that I'll need some extra time to reply to your post!

I keep a lot of site related information including all my logins in Roboform's database - I prefer to keep that on my PC rather than using its cloud version 'Everywhere' - but that has to be available on my PC because it's my means of opening sites and filling login data automatically. It also supports simple notes.

Truecrypt and others:
3 Alternatives to the Now-Defunct TrueCrypt for Your Encryption Needs