The SVCHOST exe is a program built into windows 2000 and XP that acts as a container for the various DLL services (like disk and network management.) The problem doesn't lie in the EXE, but the services that it is hosting.
You can see some of the servicse your XP machine is running with this:
Start > Control Panel > Administrative Tools > Services
Some are mandatory for Windows execution bu some just take of memory (like the Messenger service.)