I have been experiencing the slow file copy problem on the Vista installation on my Shuttle SB51G, which is my “media center” PC – it is connected to our Sony KV-36FV1 television.
My network topology looks like this: I have a Linksys WRT54G ver.2 running DD-WRT v23 SP2 (09/15/06) vpn and a Linksys EZXS55W 5 port switch. Connected to the router and switch are the Shuttle, a Sony laptop running Windows 2003 Server SP2 (the domain controller), a Toshiba Portege connected via WiFi, a Dell Inspiron 700m connected by Ethernet, an Apple Powerbook G4 12″ (rev. A) connected via WiFi, a Bootcamp (really, rEFIt) Apple Macbook (Late 2006 – MA701LL/A) connected by Ethernet and WiFi and an Xbox 360 connected by Ethernet.
The main symptom for me was the Calculating remaining time dialog box that would not indicate the remaining time for a file copy. I tried the solutions I found by searching for “Vista slow file copy”. Microsoft has a Support Knowledge Base article, KB931770 that describes their solution and offers a Hotfix, which did not work for me.
I ticked the setting (in the Folder Options/View/Advanced Settings) Always show icons, never thumbnails. As Monty Hall and Keith Linford always said, “No Deal!”
I tried turning off Remote Differential Compression, in Control Panel/Programs and Features/Turn Windows Features On and Off/clear check on Remote Differential Compression. No deal.

It did not seem like a PATA controller problem, where a second device (such as DVD drive) was on the same channel as a hard disk. My second hard disk was on its own channel and I still had the slow file copy problem to that disk.
Since I was sometimes getting an error -36, copying files from OSX to Vista booted on the Shuttle, I tried changing the Vista Security Settings/Local Policies/Security Options/ to:
Domain member: Digitally encrypt secure channel data (always) – Enable
Domain member: Digitally sign secure channel data (when possible) – Enable
Microsoft network client: Digitally sign communications (always) – Disable
Microsoft network client: Digitally sign communications (if server agrees) – Enable
Microsoft network server: Digitally sign communications (always) – Disable
Microsoft network server: Digitally sign communications (if client agrees) – Enable
All these settings did not resolve the problem.
What solved the problem? Updating the Realtek (RTL8139/810x) Ethernet Driver from Realtek to version 6.104 for Vista.
You may be thinking, “Why didn’t he try that first?” – I did. But in early June, the Realtek driver was only up to version 6.103, which did not solve the slow file copy problem.