How to measure actual memory my app uses?

I've been trying to figure out exactly how much memory (RAM) my application uses. But it's very confusing, because there are so many types of memory. I am using Windows 2000. I looked in two different places: Task Manager and a program called TaskInfo2000. What I need to know is which one of these values is the actual memory usage, and what the difference between the types is. Here are numbers:

Windows Task Manager:
Process Mem Usage: 9476KB
But when I open and close the program, the total mem usage only changes by about 4000K.

TaskInfo 2000:
Working Set KB: 9552KB
Virtual KB: 57992KB
Page File KB: 4532KB
Private KB: 4532KB
The system's Free Physical KB changes by about 5600KB.

So what's the difference between Private and Working Set? How do I know how much my app really uses? I'm sure one of the Gurus can help =) Also, is there a tool or program that measures exactly how much memory an app uses that anyone can recommend?

Also, how come no memory is freed up when I unload a form or set it to Nothing?

Thanks in advance!

C'mon...someone's gotta know something about memory, or can point me to a resource that explains it.

Another thing - do exe packers/compressors really negatively affect memory usage?

Thanks!

I think that I can help you out (maybe), is your program big, or small?, also unless its huge, you can use like 1MB Ram, cause thats all the memory that most of my simple programs use. You have to estimate to see how much your really need. You should go see the minumum requirements on diffrent programs, and then find a program that is similar size to yours, and see how much ram it requires.

Thanks...well it's pretty big, and I know exactly how much memory it uses (the numbers posted above) but I'm not sure which one of them is the number I should be using.