Cheyenne1212 is perfectly correct

You might have "heard something" about the Welchia/Nachi worm that is associated with svchost.exe? This is a fake that it creates in the ..../wins/ directory. NOT to be confused with the legitimate version in your system32 directory. If this is a worry, just update and run your AV, and apply the latest OS patches.

Your "services" tend to be grouped, with each group having a seperate instance of svchost running it.

If you feel that the amount of memory being used is excessive it could be that you have allowed stuff to register itself as a service and start automatically on boot-up, that you don't really need?

I should not worry about it unless you are getting out of memory errors though, as I have always taken the view that 256Meg of RAM that never gets used might as well be in your desk drawer

Hope that this helps.