samba - May 2002 - slow send samba->w2k

i m running a redhat linux 7.3 .. with samba 2.2.4; i noticed the speed goes 
ok if i download smb->w98 but it goes to 1/10 if i download smb->w2k...
result : samba shares from w2k are toooo slow, how to solve this problem?

Thanx in advance