Win10 hangs after boot?

I gave my dad a new notebook from Dell. The hard drive (SSD) I have specially purchased because only one HDD was inside. Windows 10 installed on it, a few programs on it. Now I want to start the computer, the desktop loads completely and then hangs up immediately. If I press the power button for a long time, the computer will shut down. If you drive it up then you can use it without any problems, nothing hangs up. Have ever one of the two memory modules already expanded and it behaves unchanged. Drivers are up to date. If someone has an idea approach, please report.

CMOS already reset, possibly the boot order in the BIOS adjusted. He is still looking for the old HDD?

As I said, he comes in to Windows. The desktop loads and then hangs up. I'll try to reset the CMOS. Anyway, thanks for the answer

With "hang up" do you mean the PC responds to nothing more?

May be a faulty installation.

Reload ISO and reinstall.

Otherwise, boot into Safe Mode and see what's in the Event Viewer.

First boot in Safe Mode (F8 at startup) and run the "Automatic Repair".