On all Windows machines there seem to be a number of svchost.exe processes running. What do this processes do and why are so many running?
I've written a lengthy explanation of what this process is, and how to figure out what each one of them does.
The bottom line is that svchost is a process that contains all of the Windows services. Since there are many Windows services, there are also many instances running.
The easiest way to check on these is to use Process Explorer:
svchost is the process which runs all the services on your computer. Each service that runs gets its own copy of svchost, which is why there are so many copies running.
The How To Geek has some more detailed information.