Incomplete install procedure

[Rishton52]

Apologies. Another post from me...
Just installing some different software. The PC decided it needed to restart. When it restarted the message on the screen was -

Attempting Boot from USB Device
BOOTMGR is missing
Press Ctrl+Alt+Del to restart

I did that, then F9 during POST to select boot from the main HD (a SSD)
So that suggests to me that the files on the USB are incorrect, or there is something missing.

[David (PassMark)]

A missing keyboard or mouse should not stop a PC booting. A lot of servers are run like this.

Can you post a screen shot from what you see on your USB drive (the files on the drive).

[Rishton52]

2 folders, 1 PDF. Folders expanded to show what's in them. Windows folder just one .tar.gz file. syslinux 4 files.