I’ve been struggling since I built the new machine in March 2009 to resolve an issue where connecting/disconnecting a USB drive would change the Disk boot order giving a BOOTMGR not found error.
The machine is a reasonably standard Core i7 built around the P6T motherboard. The only significant difference is the organisation of the disk drives.
I bought 2 off Samsung HD753LJ and 2 off Samsung HD103UJ for the machine and these are arranged with the 2 HD753LJ as a RAID 0 set for Swap and one of the HD103UJs as C: (System) and the other HD103UJ disk as D: (Data)
Despite running the latest BIOS, patches, drivers, etc… if I plugged a USB drive in and then later rebooted the machine, or unplugged a USB drive and rebooted the machine, it would always look at place the ‘Second’ HD103UJ drive (D: Data) first in the list of Hard Drives and would fail to boot.
If I then booted in to BIOS setup; set the ‘First’ HD103UJ (C: System) as the first drive and rebooted, the machine would boot in to the OS correctly.
I did log a call with ASUS, but they couldn’t understand the problem and wanted screen-shots (quite tricky to achieve from a POST screen).
Today (so it’s taken me a long time to figure this out!), I noticed that the ‘First’ drive was in SATA port 4 and the ‘Second’ drive was in SATA port 3… So, I physically swapped the order of the disks and put the System disk in port 3 (the lower number of the two).
Machine now boots fine! I can now add/remove USB drives without affecting the disk boot order.
