Memory Leak Dilema

You're obviously running Windows. If you can share the version, service pack level, etc. along with your hardware configuration, it may shed more light... If you're using a version of Windows -- legitimate copy [for WGA "windows genuine advantage" verifications during OS updates and downloads] -- that includes [ICF] Internet connection firewall, then ensure that it is enabled, as it sounds like you may have a malware, i.e. sypware, or even rootkit "infection" that may be responsible for your system's erratic behavior. You might want to download the latest [free] versions of Grisoft AVG, Spybot S&D, Ad-Aware (SE Personal), and a registry cleaner of your choice, to verify the integrity of your system. If you're adventurous, you can give Linux a try....

Well actually, we're not dealing with a "memory leak" (code failing to release allocated memory)... but this [process] you describe as temporarily grabbing all your CPU cycles under certain conditions (probably a case of "disk thrashing" -- due to lack of memory.. which would explain the "Vrooo" sound you hear as well). Your Belarc report is indeed informative... lots of software installed on your system. Anyway, Firefox itself is known to use as much as 512MB of memory! at times.. not to mention the other memory intensive programs you have installed. My first recommendation, is to replace your 256MB module in slot 1, with a 512MB module that matches the one you have installed in slot 0. Such modules are not expensive at all, and by far would represent the best "bang for the buck" in terms of an increase in system performance for your dollars (and most likely fix your problem). While you're at it, defragment your HDD, then set your swap file [pagefile.sys] to a healthy amount (at least twice the amount of your installed RAM, so 2GB.. that is, if you follow the recommendation to upgrade your RAM to 1GB), to ensure that your apps don't become "memory starved". Next, you should run msconfig.exe, using the "startup" tab to disable any unnecessary software running in the background on your machine that could be contributing to the problem. Again, verify that your machine is free of any malware, and make sure your BIOS, OS, chipset drivers, etc. are fully updated, and that your machine is running cool enough inside the case. If you follow the recommendation to upgrade your RAM, be sure to "blow out" the inside of your machine with compressed air ( as dust on components causes heat retention) and manage any loose or unruly cables with tie wraps to ensure unrestricted air flow through your case....

note: for added performance, configure a fixed size swap file for your machine. Even without a physical RAM upgrade, an increase in your swap file size might take care of the problem all by itself. I would recommend a size of 2GB (with or without a RAM upgrade)... Enter 2048 for both the "initial" and "maximum" size in your "Virtual Memory" settings, found by drilling down deep into your "System Properties".. Advanced.. Performance.. Advanced. Be sure to defragment your drive first, before implementing the swap file change. Hit "Ok" at each point while "backing out" of the Virtual Memory settings. When you finally select "Ok" for System Properties, you'll be prompted to reboot.

technical note: well yeah, when an app like Firefox bloats out to consume a quarter gig of memory or more, it's most likely due to a memory leak in the code....