UPDATE -- I solved my problem with 100% CPU usage due to multiple instances of svchost running. I originally thought I had figured it out after removing SoundForge, the program that caused a hard crash on my laptop because CPU usage dropped to between 4% and 100% after removal. But after reboot, the system returned to 100% CPU usage. The svchost.exe (Generic Host Process for Win32 Services) is an integral part of Windows XP OS. It cannot be stopped or restarted manually. It manages 32-bit DLLs and other services. In normal conditions more than one Svchost.exe instance will always be open. Because I normally have five open, I cannot launch things such as REGEDIT or Norton Anti-Virus. This is tedious, even when using online scanning troubleshooting like RAV AntiVirus.
It's important to note that SERVICE HOST is not a bug. It is a required service. SVCHOST.exe runs runs DLLs. In my case, a DLL might be experiencing a problem or might be corrupted. These problems might be caused by viruses, trojans--or spy software in my case. SVCHOST.exe runs a DLL. If a specific DLL is corrupted, you have to identify what app is causing the DLL call. The Event Viewer helps here.
I did a line-by-line analysis of tasks running in my XP Pro operating system. I have Task Manager running in one window and have noted which services are using memory and CPU. I also open a second window for Control Panel [Admin Tools/Services] where I look at plain services, not component services. I go down the list of services and turn them off and back on while monitoring the Task Manager. In my case, systems.exe is the culprit. Time to delete the culprit.
I deleted services.exe from my System32 directory and released enough resources to run Norton Anti-Virus. It found evidence of the HLLW.Nachi.B virus, so it quarantined it and deleted it from my system. However, Norton Anti-Virus 2004 totally mucked up my mail services on my laptop, so I cannot recommend its use with Windows XP Pro.
I edited my system registry to remove any other evidence. Clean registries make faster bootups.
After patching all my Windows XP Pro services, which included installing SP1, reactivating Norton Antivirus 2004, and cleaning my Windows Registry, I lost all SMTP and POP services. Losing normal mail services was not on account of spyware, but it happened because Norton Antivirus 2004 appears to be incompatible with Windows XP Pro SP1. I've gone from removing spyware from my system to removing all traces of Norton Anti-Virus from my computer. Along the way, I've attracted more people to this blog--including persistent comment spammers from Poland--than any other topic I have ever written. There must be an enormous problem with SVCHOST.exe in the home computing environment. That means thousands of computers, infested with spy programs and connected to always-on services that are easily compromised after simple port scans. If svchost.exe has your computer maxed out, many ot its protective services simply stop running (if they launch at all).
PCVS Console -- "How to remove svchost"
McAfee -- explains how SVCHOST embeds to Registry
Anthony Quinn -- "Browser-based attacks on the rise"