Physical Memory Increase....

Hi to all

I have a graphical application
when I use it, the memory used increase, but does not decrease.
for exemple I open a dialog, I get +600KB, when I close it I get -300KB
and so on,

I use the task manager to see the performance behavior of the application,

when i use my application for 10 minutes, the physical memory in the task manager point to 90 MB, and Virtuel Memory to 137MB

BUT WHEN I minimize the application, the Physical memory become 7MB, and virtual Memory still 137MB

I made the same tests with Adobe Photoshop, I openned images, and closing them, and I remark the same behavior, if I open a 200MB image, the Physical memory increase, but when I close it, it does not decrease, and On Minimize it decrease???

My application must pass a performance test, and I don't know if this is a problem of the task manager or it's a problem in my application???

Thank you