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A friend of mine had such a problem and we found out that it was a Microsoft Security Essentials that was eating all the CPU. We removed it and everything has come back to normal again, with 2-4% CPU usage when idle.
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can u try Resmon.exe tool in win7<br />
Go to Start-&gt;type in Resmon.exe and start the tool<br />
<br />
check which proc takes maximum memory usage and take necessary steps.
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Would recommend to use process explorer to find out the faulty software.<br />
<br />
<a href="http://technet.microsoft.com/en-us/sysinternals/bb896653" rel="ugc">http://technet.microsoft.com/en-us/sysinternals/bb896653</a><br />
<br />
<br />
Also can try clean boot to find out the faulty software.<br />
<br />
Clean boot process<br />
<br />
Start-type - msconfig- click on startup tab- click disable all...then click services tab- put a check on hide all microsoft services ...and then click disable all....click ok and then restart the computer in normal mode.<br />
<br />
If everything works fine in clean boot then enable five startup items and services at a time to find the faulty software.<br />
<br />
<br />
<br />
Ded9
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ctr-alt-del.<br />
<br />
Look in process and see what is slaying the memory. Will you let us know?
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@phackwer: I'm not using Security Essentials, but anyway I'm talking about ram, not cpu.<br />
<br />
@sanjithml and jarrod_williams: I already checked with Task Manager and Resource Monitor but the processes listed all use a normal amount of memory, as stated in the description. The sum of all memory used by all processes doesn't amount to 25% of total ram, but the indicator says 100% of physical memory is used and the computer is sluggish as hell when this happens. That's what's makes this problematic, I have no way to determine which process is the culprit, at least with the usual resource monitor.<br />
<br />
I will try with process explorer as soon as this happens again, maybe also process monitor to see if there's something quirky going on.
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Something is holding onto the memory. Does it only happen when &nbsp;Firefox &nbsp;is open? or does this happen with other programs aswell?
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Of course you need to try the tools when the problem occurs else you wouldn't find the culprit.<br />
<br />
Just observe the time at which it happens. some times virus can be active only on particular time and cause the problem.<br />
if it happens daily at particular time then it can be malicious virus.<br />
<br />
Keep that in mind too.. and let me know the status.
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@sanjithml: of course I used the tools while the problem was happening, that's why I posted here. It's a strange thing when no process seems to be using too much ram, and yet the memory is maxed out. I will check if the time is always the same when it happens.<br />
<br />
@jarrod williams: I usually have Firefox open all the time, so yes I'm almost positive it always happened with Firefox open. I read on some forums that Firefox 4.0 has a memory leak problem on some systems. Should a memory leak show up in Task Manager as an abnormal amount of occupied ram, or does it work behind the os' back and hide the true amount of utilized ram?<br />
<br />

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i see.<br />
i suggest you use security task manager also.<br />
<br />
<a href="http://www.neuber.com/taskmanager/taskmanager.html" rel="ugc">http://www.neuber.com/taskmanager/taskmanager.html</a>
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Have you checked in the event log for any dodgy errors or warnings? that could help narrow the search?
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Yes I checked but there was nothing strange around the time of the problem. There are no errors or warnings for the whole morning.<br />
<br />
I'll check out that security task manager, looks very interesting.
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Which AV are you using and are you running any products such as LanDesk or Altiris?
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The Antivirus is G Data Antivirus 2011. No I'm not using LanDesk or Altiris.
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If no tasks are listed that are eating up your ram then I would worry about a rootkit virus which has the ablility mask itself.<br />
<br />
When I run into rootkit viruses that are being missed by the antivirus I remove the hard drive and install it as a secondary drive in another system. &nbsp;That way the virus is not running and therefore cannot mask itself. &nbsp;I empty all the temp folders on the drive then run a virus scan.<br />
<br />
Always make sure the system that you are installing the drive into has a current anti-virus so it can protect itself.<br />
<br />
I also sort the files by time and date in the Windows folders and look for any new files that don't belong. &nbsp;I then remove or rename them. &nbsp;This can get tricky because not all new files are bad ones. &nbsp;If you are not sure about a file you should search for it on the internet to see what program may be using it.
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Instead of removing the drive I booted from an external drive which is partitioned with the Sardu multiboot rescue system, I tried 3 different antiviruses (Avira, BitDefender, Kaspersky) but there's nothing of that sort.
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is it a laptop or desktop?<br />
how many memory module u got?<br />
can try with 1 module and try?
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Desktop. I will test the modules with Goldmemory and report back tomorrow.
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No bug found in any memory bank. Today it happened again, and again Firefox was open. I guess it may be a Firefox memory leak after all.
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urlclassifier3.sqlite file under Firefox profile folder can create such problems.<br />
try deleting it.<br />
<br />

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I tried deleting the file, then ran the tool. Let's see what comes out of it.
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I've had no more trouble in the last few days. The last suggestions about Firefox were right on track, thanks.
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<div class="content wysiwyg-content">
Hello, I have a peculiar problem in my W7 Ultimate 64bit install.<br />
<br />
Lately, once in a while memory usage goes up to 99-100%, and then it goes back down with no apparent reason.<br />
<br />
The strange thing is, task manager will show normal memory usage, with the sum of all processes adding to a number far below 6Gb. And yes, it is configured to show processes from all users.<br />
<br />
I initially thought that it was Firefox 4.0, because the first time this happened I closed Firefox and usage went back to normal almost instantly.<br />
<br />
But then it happened again, and closing Firefox wasn't useful, still had to wait a few minutes for the situation to fix itself.<br />
<br />
Is there a way to find out the cause of this?
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Hello, I have a peculiar problem in my W7 Ultimate 64bit install.

Lately, once in a while memory usage goes up to 99-100%, and then it goes back down with no apparent reason.

The strange thing is, task manager will show normal memory usage, with the sum of all processes adding to a number far below 6Gb. And yes, it is configured to show processes from all users.

I initially thought that it was Firefox 4.0, because the first time this happened I closed Firefox and usage went back to normal almost instantly.

But then it happened again, and closing Firefox wasn't useful, still had to wait a few minutes for the situation to fix itself.

Is there a way to find out the cause of this?

Memory usage at 100% in Windows 7

Windows 7 is an operating system from Microsoft. Features include multi-touch support, a redesigned Windows Shell with a new taskbar, referred to as the Superbar, a home networking system called HomeGroup, and performance improvements.