Different wi-fi speeds in win xp and ubintu 10.10

[garnet]

Hi
Does anyone know why I get different speeds in win xp and ubuntu for my wi-fi.
The set up:
Cable broadband 10 Mb/s, stable virgin media UK = ~ 1.2 MB/s
Download site: microsoft.com (just any random big file)
Win xp speed - ~650-750 kb/s, varying. The drivers are the lenovo's wesite (latest?) drivers.
Ubuntu speed - 1.15 MB/s, stable.
Both downloading with latest Opera.
T60 specs in my sig.

Any ideas.