Vista drops Internet Streaming Media

I have tried to post this several times but have never seen it or a cogent
answer:
I have dual boot computer with XP and Vista installed on separate, identical
hard drives.
All Vista drivers are up to date (just checked again today).
The computer connects to the router via Ethernet cabling.
In XP there is never any difficulty maintaining connections to streaming
internet media sources.
In Vista there are frequent drop-outs, rarely is a connection maintained for
even 5 minutes without halting for rebuffering. This occurs regardless of
any other programs running in the background, whether the Vista firewall or
antivirus program is turned off. This occurs with all internet sources of
streaming media, audio and video, and with all players (WMP, Real, Itunes
etc).
Vista appears able to download large files without losing connection from
internet sources.
The computer is dual core, two gigabytes of ram, correct settings for page
files etc.