If you need to perform a packet capture under Windows without having to install Wireshark, here are some netsh commands:
netsh trace start capture=yes tracefile=c:\net.etl persistent=yes maxsize=4096 filemode=circular overwrite=yes report=no
When you are done with your capture do:
netsh trace stop
This will take some time.
You will see the files under C:\net.etl and net.cab