If you were to log in, you'd be able to get more information on your fellow community member.
My experience with netscape on NT is that it leaks memory, but if you kill it the os will recover it. The trick is that when you quit netscape, it doesn't always die. If you go into task manager and look at the list of active processes, netscape will still be there even though the windows are all gone. If you select this guy and kill it manually, the memory reappears ! It seems fair to blame netscape for this, and not NT.
Also, for X servers, I recommend eXceed or eXodus. I particularly like eXceed because i can map alt to meta, and everything works.