Maybe you have already encountered the strange behavior that it takes much longer to copy large files in Windows Vista than it does in Windows XP. You thought that the change from XP to Vista would at least be not a disadvantage speed-wise but Vista somehow seems to have a problem copying large files. This happens especially with mapped and network drives it seems.
The problem is caused by a new feature called Auto Tuning which is by default enabled in Microsoft Windows Vista. What Auto Tuning does is react on changes in the network by tuning the receive windows size. The solution would be of course to disable Auto Tuning in Vista. Some users reported that disabling Auto Tuning had a positive effect on their ability to connect to services such as Windows Live Messenger which did not work before.
To disable Auto Tuning, speed up the copy process and avoid timeouts and disconnects do the following:
Open a command prompt and type the following:
netsh int tcp set global autotuninglevel=disabled
To turn it on again:
netsh int tcp set global autotuninglevel=normal
found this at: One Tip A Day
Update: Microsoft has created a support page on Microsoft Support. The company recommends to disable the auto tuning service if users experience longer than expected email download times in Outlook 2007 or Outlook 2010.
When you try to download an e-mail message from a POP3 server in Microsoft Office Outlook 2007 or in Microsoft Office Outlook 2010, it takes much longer than expected. For example, when you download a 1-megabyte (MB) message, the download process may take as long as one hour.
Additionally, when you send e-mail messages by using the SMTP server of an Internet service provider (ISP), the connection may time out. When this problem occurs, you may receive the following error message:
Task 'Main - Sending and Receiving' reported error (0x800CCC0F) : 'The connection to the server was interrupted. If this problem continues, contact your server administrator or Internet service provider (ISP).'
This problem occurs if a network hardware device, such as a router, does not support TCP Window Scaling. TCP Window Scaling is a new Windows Vista feature.
You can access the support page here. It offers a Fix It solution, which lets you make the change with a few clicks and no manual Registry editing.
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