software raid - unable to boot from a secondary plex

I want to create software raid on a "normal" way
So I got 2 disks: disk 1 ( 250 GB ) and disk 2 ( 1TB ).
Disk 1 got 1 partition with Win7 OS and disk 2 is unallocated..

So I convert disk 1 to dynamic and add a mirror to disk 2 with diskmgmt.msc
After resynching the 2 disks, i started with testing.

I reboot the system with 2 disks in it, I see 2 bootables: Windows 7 and Windows 7 - secondary plex
Now, I shutdown the computer, I delete disk 1 and try to start again.
I can't start because an error showed up: unable to boot....

How can I make disk 2 bootable? Do I missed something?

Thanks!
Triforce2000Asked:
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rindiCommented:
Make sure your 2nd disk mow is first in the BIOS boot order. Also, a mirror should normally be setup using identical sized disks...
Triforce2000Author Commented:
Thanks, but the problem is still there when i changed my 2nd disk to first in BIOS boot order..
And could it be that this problem occured because the disks aren't the same size?
rindiCommented:
I've never tried using disks of different sizes in a windows mirror. It is possible that this is the cause of the problem.

Besides that, have you made sure you have mirrored all partitions on the original disk? If it is setup as an MBR disk, the windows installation created a small partition (between 100MB and 500MB) which it needs to boot from, and this partition of course needs to be included in the mirror. If you are using GPT, then there are also further partitions, and those need to be included too.

Besides that, PC's that come with an OS pre-installed usually include a recovery partition, and if that is the case that would have to be mirrored too.
noxchoProduct ManagerCommented:
What do you mean by delete disk 1? Did you erase it or simply remove from the PC?
What you can do is booting into repair mode - command line - disk part and checking if the drive which fails to boot has a bootable partition set active.

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