use ftp if anything. you can use samba. basicly turn on samba creat a username and password. make sure you click yes when it asked do you want to allow the drives to be mounts / read and write to. (you shouldnt be able to write to them but you can copy from it to your xp hd)

then go to windows open up explorer and do \\iphere\ you should get a list of shared folders.when you click on the shared doc it should ask for the username and password you set in knoppix when you turned on smb server(samba).

you should have a built in ftp program for knoppix such as ftpd ftp-d or pure-ftpd. just open up dos or explorer and go to the ip that knoppix has (check ifconfig before hand so you know knoppixs ip)in dos

ftp ip it should ask for a username make sure you have set roots password for this and sign in as root.
you could do this with explorer just the same open up ie and type ftp://knoppixip and it should ask for a username and password.