I want to do a one-month-free-trial-version of my software (windows 32 bit). What
would be the best way to do it? The sofware is expected to connect to internet so
maybe it could fetch a key from dedicated server.

I am looking for pointer & ideas.

I know this is really a C++, not Win32 question, but I don't hang
around any C++ group, so please tolerate.

If an object is instantiated in the main thread of a program, but
allocates memory when referenced in a worker thread, should that
memory be accessible by the main thread once the worker thread ends?

Example:
I have a class (PFBitMap) that handles BMP and JPEG files. PFBitMap
uses objects in a class (PFString) that handles strings (for filename,
date stamp, etc.). When a PFBitMap object is instantiated, it
instantiates all its PFString objects.

PFString objects allocate memory dynamically (using new).

My program instantiates a few PFBitMap objects. I want to use a worker
thread when one of these objects reads a file. But I ran into problems
when the main thread tried to access the PFString objects (e.g. a date
stamp). No problems if I read files in the main thread or if I make
pre-allocate all the PFStrings.

Pre-allocating the strings seems like a good solution, but I would
like feedback.