Yes, memory leaks can occur even when you aren't running any apps, because you still have services running. As an example, if you have McAfee Anti-Virus installed. At boot-up, McAfee will load VShield and other related programs, start the services, etc. Even if you boot, log in, and then walk away from your computer, that app IS still running. Many programs require that .dll files and other system files be loaded at startup. Driver files have to be loaded. Those files may request a block of memory from Windows, temporarily use the block to lad a file, process a piece of data, etc, and then not need that block of ram anymore. However, instead of releasing the ram back to the system to offer to another program, it keeps it reserved for it's use. The next time the program needs RAM, instead of using what it already has reserved, it will request a new block. With hundreds and thousands of transaction, you can quickly find yourself without any free available memory. is it being used? no. That's probably the best explanation i can giveof a memory leak.
No application is 'perfect.' An application can only be tested so many times under a finite number of conditions. Many bugs are specific to each setup. I don't know your ful system's specs, but maybe you have an application that requires a specific copy of vbrun300.dll. That application installs that file. Then later, you install another program that needs a specific copy of that same file. Both programs decided to put the file in c:\windows\system. One of those files is not correct for your app. Will the app function? Possibly, but this could be a good example. The program still functions, but with the incorrect version of the file. Since the file version is wrong, the program is not going to run as it was originally expected, which could cause instability, lock-ups, freezes, memory leaks, etc. and, of course, maybe you just have an app that for some reason, conflicts with your video card (just an example) because, well, it just does. More than likely, this program, during testing, was not tested on a system with the same Mobo, chip, total ram, hard drive type, size, etc as you.
I hope this helps you understand a little better. And something i forgot to mention earlier...go to
www.regedit.com and look for registry utilities. Regclean (from microsoft) is usedon my system all the time, and whenever I start having a problem or troubleshoot anyone else's system, it is the first thing I run. I then run it again. and again. and again, until the program does not find any errors. ToniArts EasyCleaner is another one I use often, because if regclean doesn't find it, easy clean seems to. Pick up both of those and run them on your system. Who knows. maybe it's just an invalid reference in your registry that doesn't get called very often, but when it does, causes the system to freeze. One of these programs may remove that reference and eliminate the problem. Good luck!