What error is it showing you? is it talking about MBR or GPT? If it is and the error is at the step where you choose where to install win 10, what it wants you to do is delete all the partitions on the hard drive and then it will install win 10 on the blank space
If you have any info on the drives and can't afford to delete all the partitions, you can try to use this to save the info before formatting drive: http://www.howtogeek.com/howto/windows-vista/use-ubuntu-live-cd-to-backup-files-from-your-dead-windows-computer/