Vista - Issue with NAS transfers

Hi,

I have 2 Vista PCs and 2 XP, all connected to a WD NAS device. When I copy a folder full of files - about 800Mb - to either of the XP machines this takes about 1.5 mins. When I copy to either of the Vista machines (one Home Basic, the other Home Premium), it takes around 9 mins. I've tried switching the cables - makes no difference. I've tried disabling the firewall and anti-malware (Kaspersky) during the transfer - makes no difference.

How come Vista seems to be so much slower at coping with the transfers than XP? Both the Vista machines are <6 months old, both the XP are > 3 years old, so it should be the other way round if anything!

All the NICs are set to auto-negotiate.

Any suggestions as to what to do?

Thanks

Chris

Quick clarification - I'm talking about copying files from the NAS to the PC's.

In practice it's quicker to copy files from the NAS to one of the XP machines, then to a large USB memory stick, then onto the Vista machines. Which rather defeats the object of having network based storage....

Thx