I am using Disk Director 10 (build 2160) and have a HDD partitioned as below. ______________________ | Vista Ultimate 32-bit | ______________________ | Windows XP Pro SP2 | ______________________ | Windows Server 2003 | ______________________ DD10 was installed in Vista. I subsequently installed Windows XP and then Server 2003 at each stage ensuring the OS would should in OS selector which it did. All OS's work fine. I can boot the computer and select any and it will load into that OS fine and it's happy days. However, evey so often, OSS will deactivate for whatever reason. I cannot determine under what condition is deactivates but it just does. When it has deactivated, it will just load into the default OS which is Vista. Just after the BIOS screen finishes, there is an error MBR Error 3 before it proceeds to load into Vista. It is not a time-out setting (eg. 6 sec countdown.) becuase I have a second HDD (which is a dynamic disc) and OSS always indicates when OSS is active upon boot-up that Dynamic Disks are not supported. I must always click OK to go past this screen into the actual selector screen. I find that I can reactivate under Disk Director within Vista or the recovery CD and it will work for maybe 4 or 5 slections and then deactivate. Any ideas?