[SOLVED] Lenovo Laptop won't boot if I remove the original hard drive (now demoted to storage only)

[Jacopo_4]

Hello, I have a Lenovo Z50-70 laptop that originally came with a 1TB hard drive; a while ago I removed the DVD drive and replaced it with a 500GB SSD, where I installed Windows 10, so I started using the original 1TB hard drive for storage only.
I haven't had any problem since then, apart from the 1TB hard drive sporadically disappearing from the connected drive.
As I thought the hard drive was failing I bought a new one, but I realized that, if the original hard drive is not present, the laptop won't boot, despite the SSD with the OS being still connected.
What could be the reason?

 

[rgd1101]

did you install windows 10 with the hdd connected?

 

[Jacopo_4]

did you install windows 10 with the hdd connected?

Yes

 

[cl42]

https://neosmart.net/wiki/convert-gpt-to-mbr/i just came across an hp laptop[pavillion dv7] an acer 5134 and 2 gateway laptops.
the dv7 and acer took me forever to research help for it. the manufacturers are useless. all of the above started putting partitions and boot sectors? on the hard drives with all the "hp tools" etc. they started doing that with windows 8 and im almost positive my mothers hp 2000 i bought her is the same way. i've repaired several of my brothers laptop hard drives from being dropped to being stepped on by EMT ambulance guys. a friend whose kid saturated her laptop in mountain dew also. every one of those had the tools and a main and a recovery partition. i've never been able to successfully "save"/transfer those partitions but i'm not educated in this. its just passion/self taught

edit: it's my understanding in the past manufacturers did not include these partitions but had a website or not. i did want to add.. the hp dv7 & acer were AMD and easy as hell to work with on windows[they had REGULAR bios/mbr,it installed most drivers. the 2 gateways were intel and they had a weird NO BIOS but UEFI and GPT partition on hdd and i still can't wrap my brain around what is missing that won't let me boot and i have no clue the correct parameters to google for help but i think it's involved in this mess...GPT vs MBR...this is the best explanation

https://neosmart.net/wiki/convert-gpt-to-mbr/

i 've found for that. your lenovo had win 8 but i didnt see if it had mbr/GPT,ETC.i wouldnt know how to search for that . good luck