Solved! Fast BIOS, Slow Boot

[Shineon11]

Hi everyone, first post noob here.

I removed Ubuntu from my laptop about a month ago. All traces are gone from BIOS.
It used to take 10 seconds from pressing the power button to the login screen (before dual boot, and with dual boot), but now it takes over a minute. My BIOS start time is still 2.5-3 seconds, but splash screen to login takes an age. I did a fresh Windows install, no difference. I have nearly everything turned off in task manager startup.

I know this question's probably been asked before, but I've tried everything and would appreciate any help and advice.
Asus ROG GL551
i7
16GB DDR3L

 

[AlHuneke]

I suspect there is some dual-boot leftovers that are causing problems. There may be a way to fix that, but if you don't mind doing a clean reinstall of Windows, that will likely do the trick. Create an install USB. Do this by following the steps at https://www.microsoft.com/en-us/software-download/windows10). Select the option to make media for another computer. Boot from that and do a complete (clean) reinstall which will delete everything on the HD and make a new boot partition.