I only have experience of accessing from win95 & win98 clients as knoppix has replaced my win2000 server and I had so many issues with customers' XP systems I didnt even want to know. <that confession made me mildly sick>.
Use the samba service from the main menu...Knoppix...networking to start set up the shares for access from mswindows <washes mouth out> PCs.
most likely if you login to windows with a username of knoppix & no password you will connect straight away.