After twice fully downloading game from steam download pauses and dialogue box with (disk write error) appears. I checked and files verify 100%
(note Game is not yet in Common folder as expected)

Set files in steam SteamApp/Download/ fallout4.exe and Fallput4Launcher.exe to run as administrator and ran steam same verified 100% . On play same error.
However falout4Launcher.exe will now run direct but on clicking play I again get (disk write error)
I get no other error messages appear

Can anyone help

Disk write error Steam

did you try google?

I suppose not.

It is a file system error. You have a HD file system failure.

Read this.

https://support.steampowered.com/kb_article.php?ref=9709-FKCB-4230

TLDR. You need to run CheckDisk on that hardrive/partition where Steam is installed.

Good luck.

Might want to back up that partition/HD to another HD after you do all that.

Checked the drive (again) no issues no fault reported still get 'disk write error'

On to moving steam files (tried on 1st download and again now) the process says to backup game files. When I try to backup screen shows 'Fallout 4 cannot be backed up until it has finished updating'

Fallout 4 Game files are in SteamApp/Downloading/ and not in Steamapp/common/ as expected could sit be that final process is not completing?

This is where I was on 1st download and why I deleted and retried to download as it appears not complete I freed up more space before 2nd try just in case now have 2x required.

Do I now again delete Fallout 4 move Steam and all other games from my D: to my empty F: and re-try download

OK with no help forthcoming and about to ask for a refund I decided to have a look at files in SteamApp/downloading folder howerver I noticed a File in SteamApp/Common fallout 4 size 0k deleted it and now game runs.

This I think is a Win 10 issue so here is the fix

TLDR: To fix DISK WRITE ERROR problem in Windows 10, go to Program Files (x86)/Steam/steamapps/common and delete the 0KB Fallout file, then restart the game.