hi Euge,
please, there is no need to hurry. i guess you can at least use the hard drive from the old Windows computer you found to attach it to your current computer with PCI-Express slots and test in Windows. i'm really suspecting it's as simple as hardware fault that makes data transfer unstable and we will just need to replace the board, but it's good to confirm it first, because otherwise it's waste of time since you need to wait at least 2 weeks - one week we to receive back you current board and one week you to get the new replacement board.
regards,
cody