You can look at the file called fahlog.txt in the directory where you have folding@home installed. scroll up to where the client started and you should find the usernamd and team number it is working under there. It'll look something this:
--- Opening Log file [January 19 21:56:24]
# Windows Console Edition #####################################################
###############################################################################
Folding@Home Client Version 5.04beta
http://folding.stanford.edu
###############################################################################
###############################################################################
Launch directory: C:\Scott\Folding at Home CPU 1
Service: C:\Scott\Folding at Home CPU 1\fah504-console.exe
Arguments: -svcstart -advmethods -verbosity 9 -local
Launched as a service.
Entered C:\Scott\Folding at Home CPU 1 to do work.
[21:56:24] - Ask before connecting: No
[21:56:24] - User name: Insidious (Team 198)
Hope this helps
-Sid