svchost.exe is a common name in windows Task Manager. At any given time you should be able to see several svchost.exe processes running in the task manager. This makes the virus manufacturers to hide a process with the same name and go undetected. svchost.exe is popular name for virus makers. The legitimate svchost.exe file is located at C:\Windows\System32 folder. Most of the viruses add a file with this name at different locations. I have grouped together all those viruses that add svchost.exe on the computer. A program like Microsoft Windows Defender or Sysinternal's Process explorer can show you the actual path of a running process thus instantly determine whether the process is legitimate or harmful.
How to use Windows Defender in windows XP
How to use Windows Defender in windows VistaOr you can use Sysinternal's Process Explorer for easy detection and removal of virus processes.