Hi, I have Toshiba Satellite U500 with 4GB RAM on my machine, and I am running Windows Vista home premium 64bit service pack 2. When I start my laptop it uses about 1.5GB. The memory usage will than start raising in about 0.5GB a day, even if I do not start any process manually (of course there are many services running on startup). I tried to isolate the problematic process using the task manager, but I couldn't. After several days, the Task Manager is showing memory usage of about 3.7GB, but when I look on the processes tab, the memory (Working Set) column will sum up to about 1.1GB. The Commit Size memory sum up to an even lower number. Any idea what is killing my memory or how I can find it?

Hi Brink and thanks for the quick reply and quick answer :-) The resource monitor looks very hand, but unfortunately on my case it didn't help, as it showed the same information on the processes the Processes tab showed. I think you're right about the cache, as the memory usage is not "recorded" anywhere. The problem is that when my machine gets close to the 3.8GB is start working so slow, it's hardly usable. Is there any way to disable the Superfetch cache, to see if this is indeed the problem? Again many thanks for the help, you're a life saver!

You can disable Superfetch in Services. I also suggest you reboot. That will set it back to more normal.
But the system slowdown should not have anything to do with caching. All the cached RAM is marked as "available" when needed. There must be another reason for your slowdown.

It only happens when the memory is getting close to 3.8GB. If it would have been usable, I'd check the page faults and see it's indeed the memory, though I'm quite sure it is. If it's not the cache, any idea what it might be?

Checking the # of hard faults is a good idea. Without some more digging it is hard to say what the cause could be. When the problem occurs, it would help if you took a snip of task manager (the lower part with the numbers) and posted that here.
I would also suggest you check with Process Explorer ( Process Explorer ) which processes bring your system to a creep. Click on "CPU" so that all the CPU eaters appear on top. Then right click on the processes that consume the CPU and go to Properties. That will give you further detail. If it is a svchost.exe, hovering over the process already gives you some more info.

this will not fix your problem but it will help,add virtual memory,i have 6 gigs of RAM now,the default was 2 gigs

Virtual Memory Paging File - Change

Thanks for your help. Next time it happens I'll check out the page faults, and CPU, though I'm 100% possitive this is a memory issue. BTW, I was using WebShots screen saver and after hearing about superfetch, I wonder if it's the combination of the two causing the problem (superfetch starting to upload 500-600 images of 2-3MB each to the memory). Anhyone using Pixasa, Webshots or any other image rotating screensaver successfully?

Page faults were 50-100 faults/sec, this is definitely memory. I disabled superfetch, let's see if there is any improvement... :-|

With that amount of RAM you should have no page faults at all - or very few. On this system where I am on right now (3GB of RAM), I have zero page faults. But Superfetch should not be at fault. All the cached memory is marked as "available" and should be useable when needed.
It would help if you posted a snip of task manager > Processes tab > click on "Memory" so that the heavy hitters are on top.
Also, what are your numbers in task manager > Performance tab behind "Commit(MB)", just above the Resource Manager button. Maybe your page file setting is wrong.