To answer your first question, yes, it's possible. But take note
that if you never reformat it again, your hard disk space will
shrink.
For example, you have 80GB. 50GB for system, 30GB for other
drives.
Deleting the 30GB will make this an unpartitioned space. Windows
will still recognize the 50GB and show only 50GB after you
reinstall Windows.
Second question: Without using any other softwares, there's no way
you can delete a partition without reformatting and reinstalling.
With third party softwares, yes. That's through Partition Magic, as
sillyme has said.
Third question: As long as your system specs never change, Windows
won't prompt that this product is an imitation. Rather, it will
prompt you to activate, failing which will lock you out of Windows.
This only applies to OEM copies of Windows. Volume-licensed copies
of Windows don't need to activate.
