W2k vs WinXP with ADSL

[napocska]

My problem that I had 2 computers (similar hardware, Duron CPU, Via chipsets, Via USB Hub). One is running W2k other is running WinXP Home Edition. I subscribed for ADSL 256kb/s service. ISP gave me an Aztech DSL500U modem(using Alcatel chipset). I set up the drivers on both PC and i didn't change any settings.
Then i plugged modem to PC running W2k. Connection speed was 10Mb/s (downsized at ISP to the given speed) and download speed was around 25kB/s (close to limit).
Then i turned off PC and plugged modem to the other one running WinXP. Connection speed was between 1 and 3.4Mb/s and downloading the same file from the same location happened on 13kb/s.
Then i checked settings with TCP/IP Analyzer. All numbers were the same...
Any idea what made the difference? I checked up registry HKLM/.../Tcpip/.../Interfaces/.../AtmArpC/MTU was 9180 on both machine. I can't find any obvious difference in settings.
I can post screenshots about my WinXp settings if it helps.
Thanks for any idea.

[Andrzej]

very interesting observations
I'm surprised

2k>>>xp in kbps
and
2k>xp in kBps
on the same line & modem, both USB hube
you explain that setting are the same
and default in both..
hdw is similar...

would you kind explain hdw in both PC
cpu, ram, hdd, page files
for 2k pc
and
for xp pc

[Cypher]

XP sux hence the penguin calls .