Windows – SVCHOST.EXE (LocalSystemNetworkRestricted) is using almost 100% disk usage

This annoying system pig-out is caused by a Windows Vista mis-feature (piece of crap) called SuperFetch. While the service still exists in Win7 it's been fixed up and doesn't seem to slow me down anymore, although your mileage may vary.

http://en.wikipedia.org/wiki/Windows_Vista_I/O_technologies#SuperFetch

After disabling this crap-fest, from the Services window (type Services into the start menu search box, find Superfetch, stop it then disable it from auto-starting), these freezeups go away. On systems with sufficient RAM and disk-throughput, superfetch results in a net increase in system performance. On my laptop enabling SuperFetch results in periodic freezes of the system where it doesn't respond at all to mouse clicks. I thought I was going crazy, but it was part of the stuff that the people who brought you UAC and other great innovations threw into Vista. I think it's been reworked or scrapped in Win7 so it won't do this.

Update Commenter says he sees this in Win7. I have yet to encounter a problem with Win7 on laptops, but then all my laptops have very high performance 7200 RPM drives or hybrid or solid state drives. I would like to hear in comments from people who have this problem with SuperFetch slowing down a DESKTOP machine with a 7200 RPM conventional drive, or SSD. (I could imagine this happening on a dog of a hard drive with a 5400 RPM spindle rotation speed.)

Update2 Part of the problem with Windows is that it only reports parent process svchost.exe, and you need to read the other answer below that points you to the SysInternals Process Explorer too, which helps you to find out what actual thing inside svcchost.exe (like superfetch or windows update or something else) is actually slowing your machine down.

Superfetch is a service that was introduced with Vista and has been part of Windows ever since. It tries to speed up your computing experience by pre-loading parts of programs into memory with sometimes detrimental effects as you had to experience. It tries to determine which software you use and stores parts of it to the Windows folder.

Unfortunately, Superfetch doesn't always get it right which software you're going to use and can keep your hard drive busy for minutes after booting. I found it especially annoying since it kept on loading software I wasn't even going to use or that I had only used once. Since I use a plethora of different programs every day, Superfetch actually had a massive negative impact on my computer's performance with keeping the hard drive busy for 5-10 minutes after a fresh boot. This is the very reason I have been running Windows with deactivated Superfetch ever since it came out.

Additionally, since Superfetch uses memory for applications you might not even run, your free amount of memory will take a hit and might result in more swapping which adds just more wear to the hard drive.

Here's how to deactivate Superfetch:

• Open up the Run prompt and enter Services.msc.

• Find Superfetch in the list, right click it and stop the service.

• Double-click on it and set its start up type to Disabled.

Once you reboot, Superfetch will stay inactive. Other culprits that may also slow your hard drive down can be automatically scheduled defrag sessions as well as Windows Search Indexer. You can deactivate the latter the same way as Superfetcher.

Svchost.exe is the executable that runs the service. You don't really have to mess with it after deactivating Superfetch. In fact, you should not touch it at all since it runs a lot of crucial Windows services.

You can check the Prefetch folder in the Windows directory to see which programs Superfetch prebuffered in your memory. You can safely delete them once Superfetch has been deactivated.