I tried installing Ubuntu 16.04 on Precision 5520 (Windows 10 is pre-installed) I got stacked because the ubuntu installing program could not find the hard disk.  However, by changing a SATA mode in BIOS to 'AHCI' as the instruction of the web page, I managed to install Ubuntu 16.04 on Precision 5520 with Windows 10.  [URL]
Hello,
Precision 5520 -install Ubuntu over windows?