Started getting "BootMngr missing or corrupt" message again on initial powerup
Will fiddle around in BIOS
Bro67 - tried new cable

Thanks so far for suggestions

No, will look into it.
It's almost like the drive(s) boot to slow for the motherboard posting - and by doing second reset the drive has spun up to speed and BIOS is able to read Boot file (probably...

I cloned Win 8.1 (working flawless) to new drive, this then ran for about 2 months before I upgraded to Win 10 (online upgrade) this ran okay for about 30 powerups and then started giving issues....

This is the second drive doing this. This drive being a month old. Thats why ive tried new sata cable and port

Think im being miss understood. By Btmanager i mean BootManager file

No no torrent apps installed. Message appears straight after bios mem test.

If I start my PC I some get either one of these error messages straight after post - "The file is possibly corrupt. The file header checksum does not match the computed checksum" or "BTmanager...