KB2604121+KB2468871 update failure+ SFC /scannow failure to repair

Stopped at the first hurdle: reboot and F8 as usual brings up list of disks.
Without giving full details:---

HDD: an old Seagate; HDD: another old Seagate; HDD: 3m-WDC WD640 .... OS7 system;
CDROM: 3s-PIONEER DVD-RW DVR-21 .... OS7 .iso;
USB: WD My Passport 0740 1022; USB WD Virtual CD 0740 1022;
USB: WD SES Device; IDE: Initio A:WDC WD640.....

Thinking maybe there was an Advanced Boot menu beyond this, I restarted and F8'ed past the Boot up menu but no go as you no doubt would know.

No 'Repair your computer' unless it's in any way connected to the Virtual CD? The My Passport disk is password protected, not opening at startup: whether that accounts for the Virtual CD listing I'm too ignorant to know.

Hi NoelDP back yet again,

I've gone back to your penultimate instruction: I had left the iso Windows 7 +SP1 DVD in the player. This resulted in F8 producing my boot options, 'Esc' for default boot plus F8 produced the Advanced boot - but no Repair Disk.
However removing the DVD and repeating the process did produce the required option.

The result of the Command Prompt was as follows:

Deployment Image Servicing and Management tool
Version: 6.1.7601.17514
Image Version: 6.1.7601.18489
The scratch directory size might be insufficient to perform this operation. This can cause unexpected behaviour.
Use the /ScratchDir option to point to a folder with sufficient scratch space. The recommended size is at least 1024 MB.
Reverting pending actions from the image ---
The operation completed. Any revert of pending actions will be attempted after reboot.
The operation completed successfully.

I'm certain this will make more sense to you than it does to me.

Assuming by windows folder you either mean the system file or the OS7 installation, the drive is C:

I repeated initial DIR C:\

then

DISM /Image:C:\ /Scratch-Dir:C\ /Cleanup-Image /RevertPendingActions

resulted in

Error: 87 The scratch-dir option is unknown.
For more information refer to the help by running DISM.exe /?_
The DISM log file can be found at X:\Windows\Logs\DOSM\dism.log

NoelDP,

You underestimate my ignorance and decrepitude (age 77): I 'googled' UAC but RE? Religious Education?????

Which drive should be the target drive? My Windows 7 SP1 is on drive C:, the Windows 7 SP1 derived from the iso file is on E: which is a Pioneer CD DVD player/recorder.

All other disks are devoted to storage and backups.

If I'm to check for usual files in the target drive can you give any guidance which it might be?

Apologies if I'm slow to understand, but how do I recognise which drive is used by the RE?

On drive C: there is a file which is new to me $Windows.~WS date modified 05.08 is that what I'm looking for?

There are also 4 files with complex mixtures of numerals and lower case letters, modified 20.07 which I assume originated with Ashray of Microsoft since that was the date he was 'messing' with things: each of these registers as empty.

There are also 3 similar empty files on my drive G: but dated 05.08 and 08.08.