XP Traffic Speed Monitor?
 

Any way I can see total bytes transferred / current traffic speed on my NIC on XP? Some free software?

Press <CTRL> + <ALT> + <DEL>... see Network-tab :winkwink:

Keep the Taskmanager open but minimized during Your session and it will keep the data...
You might want to do this also:
Go to the Network-tab and then hit "Show..."-menu and select "Select/choose Columns" - Lots of useful stuff for monitoring.