Windows 7 and Ubuntu

Hi all,
my first post ... eh eh

I have 2 windows 7 Ultimate PC (A and B) and an Ubuntu 10 machine (C).
A: W7 - Intel Core2 Duo E8400 @3.0GHz - 2G RAM - Gigabyte MB - Realtek integrated NIC
B: W7 - Intel Atom D510 - 1GB RAM - Gigabyte MB - Realtek integrated NIC
C: Ubuntu - Intel Core2 Duo E4600 - 1GB RAM - Realtek integrated NIC

The problem is the transfer speed between B and C.

Here the transfer speeds:
A->B (Samba) = 45MB/s
B->A (Samba) = 60MB/s
A->C (FTP or Samba) = 60-70MB/s
C->A (FTP or Samba) = 60-70MB/s
B->C (FTP or Samba) = 20-25MB/s
C->B (FTP or Samba) = 15-17MB/s

It looks ilke that the B computer does not like the C computer. All the other transfer speeds are good enough for me.

What can I do to identify where the problem is ?


thanks to all.