Hi,
Welcome LinuxQuestions.org
you need to read
www.samba.org for more information how to shar files. Also, check following link at:
http://www.linuxdocs.org/HOWTOs/SMB-HOWTO.htm
about voice chat, i think you need to visit following sites.
http://gaim.sf.net
i haven't trited this. Also, check this one :
http://teamspeak.org for Widnows and Linux client.
hope this helps.
--Hitesh