FTP install for a newbie

[Guillaume Viguier]

Hi,
I'm trying to install FreeBSD on an old computer (without any cdrom drive) linked to another computer (running under Windows xp) through a network cable. I downloaded the iso files on ftp.freebsd.org and extracted them on my hard drive. I set up an FTP server on Win xp pro (with Cerberus FTP Server) to use the FTP install mode of FreeBSD through my network cable. Everything works fine at the beginning, except when it tries to install the packages or the ports. I can see on my FTP server that the commands FreeBSD sends to receive the files are wrong. FreeBSD sends:
RETR packages/All/xxx
xxx being the name of the package. 
When FreeBSD sends that, the server answer that the file does not exist, because I think the command should be:
RETR packages/All/xxx.tbz
I tried that command with my Windows ftp client and it works. But I don't know how to set it up in FreeBSD...
Thanks a lot for your help, and sorry if my english is not very good.