What's a good program to test file transfer speed across a network?

I'm looking to compare various NAS solutions but I'm looking to speed the total speed obtained across a network.

I'd also like to test my local hard drives...

Is there anything easy / stable / reliable that will work for Windows XP and Vista?

Thanks for any suggestions!

If i remember correctly i believe atto can test drives over the network. This will give you a pretty accurate test