Hi John
Thanks for trying to help, I really appreciate it, but I've done all that and it makes no difference.
Here's what I've tried so far:
Remove all USB devices except keyboard & mouse
Disable all startup processes except Microsoft's
Uninstall all protection software (Spybot, System Mechanic, BitDefender, WinPatrol etc)
Created & run the following batch files:
net stop wuauserv
rmdir /s /q C:\Windows\SoftwareDistribution\DataStore
rmdir /s /q C:\Windows\SoftwareDistribution\Download
net start wuauserv
pause
net stop bits
net stop wuauserv
net stop appidsvc
net stop cryptsvc
Del "%ALLUSERSPROFILE%\Application Data\Microsoft\Network\Downloader\qmgr*.dat"
Ren %systemroot%\SoftwareDistribution SoftwareDistribution.bak
Ren %systemroot%\system32\catroot2 catroot2.bak
sc.exe sdset bits D:(A;;CCLCSWRPWPDTLOCRRC;;;SY)(A;;CCDCLCSWRPWPDTLOCRSDRCWDWO;;;BA)(A;;CCLCSWLOCRRC;;;AU)(A;;CCLCSWRPWPDTLOCRRC;;;PU)
sc.exe sdset wuauserv D:(A;;CCLCSWRPWPDTLOCRRC;;;SY)(A;;CCDCLCSWRPWPDTLOCRSDRCWDWO;;;BA)(A;;CCLCSWLOCRRC;;;AU)(A;;CCLCSWRPWPDTLOCRRC;;;PU)
cd /d %windir%\system32
regsvr32.exe atl.dll
regsvr32.exe urlmon.dll
regsvr32.exe mshtml.dll
regsvr32.exe shdocvw.dll
regsvr32.exe browseui.dll
regsvr32.exe jscript.dll
regsvr32.exe vbscript.dll
regsvr32.exe scrrun.dll
regsvr32.exe msxml.dll
regsvr32.exe msxml3.dll
regsvr32.exe msxml6.dll
regsvr32.exe actxprxy.dll
regsvr32.exe softpub.dll
regsvr32.exe wintrust.dll
regsvr32.exe dssenh.dll
regsvr32.exe rsaenh.dll
regsvr32.exe gpkcsp.dll
regsvr32.exe sccbase.dll
regsvr32.exe slbcsp.dll
regsvr32.exe cryptdlg.dll
regsvr32.exe oleaut32.dll
regsvr32.exe ole32.dll
regsvr32.exe shell32.dll
regsvr32.exe initpki.dll
regsvr32.exe wuapi.dll
regsvr32.exe wuaueng.dll
regsvr32.exe wuaueng1.dll
regsvr32.exe wucltui.dll
regsvr32.exe wups.dll
regsvr32.exe wups2.dll
regsvr32.exe wuweb.dll
regsvr32.exe qmgr.dll
regsvr32.exe qmgrprxy.dll
regsvr32.exe wucltux.dll
regsvr32.exe muweb.dll
regsvr32.exe wuwebv.dll
netsh winsock reset
netsh winhttp reset proxy
net start bits
net start wuauserv
net start appidsvc
net start cryptsvc
pause
dism /online /remove-package /packagename:Package_for_KB2919355~31bf3856ad364e35~amd64~~6.3.1.14
pause
dism /online /cleanup-image /startcomponentcleanup
dism /online /cleanup-image /restorehealth
pause
(I put a pause at the end of each so I can review the results)
Some updates installed after all that, but not the infamous and necessary KB2919355.
I've run sfc /scannow plenty of times and it reports no problems. Dism runs OK and again reports no problems.
So I've given up and reinstalled all my software. Unless anyone comes up with something I've not tried I'll just have to wait for MS to sort out this debacle, or Windows 8.2 comes along (better still Windows 9). But I am now seriously considering a Unix-based OS instead - I can do without this aggravation.