I store all my files on a Synology NAS which is accessed using several computers in a common workgroup-based (wired) IPv4 network with static IP addresses. I have been using Windows Vista for accessing the NAS which has been working perfectly for years. Neither NAS nor PC client hardware have been changed since. Some weekes ago I upgraded my workstation client to Windows 7 Professional x64. This is exactly when I noticed that suddenly more and more images on the NAS had visible errors (JPEGs with wrong colours and weird blocks) and more and more MP3 files had audible klicks and damaged covers. In addition my Outlook PST files were also damaged and could sometimes not be fully repaired. This all only happened to files stored on the NAS, never to local ones on the workstation. Apart from that the network connections and NAS visiblilty work perfectly. I then found out that if I changed my network settings from "Home" to "Work", it got somewhat better with fewer errors. But still when I copied e.g. images from HDD to the NAS with the Windows 7 client, half of them gets damaged and I have to try to re-copy them a few times until it works. And Outlook still breaks with PST access errors. What could this be? I repeat: the files were not damaged before and could be accessed without any problem when using Windows Vista. I already tried every possible configuration option, disabled energy saving options of the NIC, disabled task offloading, disabled IPv6, and so on. Nothing worked apart from the minor "Home" to "Work" optimization. I cannot be that Windows 7 keeps damaging my files, can it? Has anyboy a hint or a solution? Thanks in advance... Edit: some additional details about the system: Workstation: Asus P5B-E with on-board Atheros L1 Gigabit NIC, 4GB Kingston HyperX, Intel Core2Quad Q9400, HDD Samsung HD103SJ, nVidia GeForce 8800 GTS 512, Windows 7 Professional 64-bit with all available updates NAS: Synology DS109 with latest DSManager 2.2, HDD WD20EADS, over Gigabit LAN (D-Link GDS-1005D)

the drive(s) / networking jack in the nas could be bad..it does happen.I would not be looking at windws per say, but I would be looking at the network cards driver.

Based on your hint I mounted an old 3com 3C2000 card into my Windows 7 workstation, and now the network really seems to work without errors. So if it isn't a hardware error on my motherboard (which I don't believe as it worked perfectly with Windows Vista), the Windows 7 driver for the on-board Atheros NIC is really ____ and dangerous... Thanks for your precious help.