I'm running 32-bit Windows 2003 R2 in VMware 6.0.3 on my Windows XP 32-bit host OS. I have run all the Windows updates, but haven't done any other tweaking. About once every hour (but not quite on a schedule) my CPU usage goes to 100%, slowing everything down for about 1 minute. When I can get taskmgr up, I see that usually a process called "SYSTEM" is using most of the CPU. Occasionally taskmgr itself is using up almost all of it. What is causing this, and how can I avoid it?

The host machine is an older Pentium D with 3 gigs RAM. The VM is running from a relatively fast SATA drive. Memory usage in either the host or the guest doesn't seem to be a factor in whether or not these slowdowns will occur.

thanks! Chris

+1  A: 

I happened to stumble across the same problem you are describing, one of the processes of vista itself that uses all, or most, of the CPU resources for a few seconds to return to normal afterward, and back again. It wasn't my own computer so at first I hadn't a clue of what was installed recently, if the problem did occur before but was never noticed etc, so I had to go look and see if others might have the same problem

As it turned out it was a misbehaving driver of one hardware components that caused the problem, unfortunately the driver wasn't updated yet so I couldn't fix the problem entirely, (disabling did help though)...

However you are using VMware thus a driver issue is, i think, rather unlikely. of course you never know.

I'll second that. Drivers run as the OS level. Lately they are getting worse and worse. Especially the cheap knock off hardware with unsigned drivers.
Great Turtle
I don't know if there is a similar app on XP that the "Performance Monitor" on Vista, but it could be very useful to find wich particular process/service is causing trouble. It is also very easy to see what process use your hard disk or the network... I think your problem is more specific to VMware... I'm having an issue on my Dell XPS M1330 with VMware server on Vista : first launch => 5 min freeze !! (lot of swapping, pagefile is full, ...) others have the same problem.

It might be a Windows Update service - I've stumbled at it several times, but only when the host didn't have CPU VT capability. I'm not sure whether your Pentium D supports Intel VT, old Pentium D's do not.
Try turning off automatic updates and see if it helps.

As a workaround, try granting the virtual machine two CPUs. One will still be hanged by outlawed SYSTEM process, but second CPU will handle everything else just fine.