Vsmon.exe is part of the Zonealarm firewall. And I'm sure it monitors something, but I don't know what. If you've installed the SP2 update of Windows XP and fully enabled the new firewall, you can consider to uninstall Zonealarm, in my opinion.
Hope this helps.
can anyone tell me what this process is doing ? i see it running in task manager and at times it seems to be consuming an awful lot of system resources.