Hi,I am testing my application on Windows 7 Ultimate 6.1.7.7000 Build 7000 installed on a x86-64 box.Some details of the machineSystem Manufacturer HPSystem Model ProLiant DL380 G5System Type x64-based PCProcessor Intel(R) Xeon(R) CPU 5160 @ 3.00GHz, 3000 Mhz, 2 Core(s), 2 Logical Processor(s)BIOS Version/Date HP P56, 1/24/2008SMBIOS Version 2.4Installed Physical Memory (RAM) 2.00 GBTotal Physical Memory 2.00 GBAvailable Physical Memory 1.38 GBTotal Virtual Memory 4.29 GBAvailable Virtual Memory 3.57 GBPage File Space 2.29 GBPage File C:\pagefile.sysThe system has 4 disks presented to it from an external storage array. My application runs "mountvol /n" to disable automatic mounting of these disks. It uses IOCTL_VOLUME_ONLINE to make the volumes online. The GetLastError() returns 0 when this IOCTL is issued but it fails to bring the disk online as the subsequent format command on the disk fails with "Device is offline" error.IOCTL_VOLUME_ONLINE was working without any issues on Windows Vista and Windows 2008 Server.Is this how IOCTL_VOLUME_ONLINE is supposed to behave in Windows 7? Is there any alternative IOCTL?thanks and regards,Praveen

Hi, Since this is a program development question, it is better to create a thread in our MSDN forum. msdn Microsoft Development, MSDN Subscriptions, Resources, and More Arthur Xie - MSFT