I have neglected to say how much memory can be addressed by the 80386 in 32-bit protected mode (the mode used by Windows NT). The answer is a whopping 4 GB. Not only is it 4 GB, but each application running in this mode has its own 4-GB address space, which should be more than enough memory for even the most demanding of applications. The only problem is that memory isn't free. To purchase 4 GB of memory would cost approximately $204,800 at the time I'm writing this.
Most of you probably can't afford to walk up to your nearest computer store, lay this kind of money down on the counter, and push a wheelbarrow full of RAM back to your house. Besides, even if you could buy all this RAM, where would you put it? It certainly wouldn't fit in any 80386-based computer I've ever seen!