SFC scannow offline

This is my first post on this excellent forum. I have been trying to run a sfc scan, both online and offline, but neither will get very far before the system cancels them.
I read up (here as I recall) on how to run the scan offline. So far I have named 'C' as both offbootdir and offwindir, but I think this may be wrong.
I am attaching an image of disk mapping for what I believe is my 'hybrid' Asus s550cb notebook, running win 10, fully patched except the recent update (KB4074588) which will not install properly. As part of my system, there is a small SSD drive in addition to what is revealed by the attached image.
My question is, how to know which drives I should name for the sfc scan from boot. The image reveals only C & D with assigned drive letters, with D containing only personal data. Disk management does not allow assigned letters to the other partitions, so if I need one of those, I seem to be unable to run the sfc scan.
Any help with this will be much appreciated.
Thanks and regards to all.

Thanks. I have now used a boot disc which i made a while ago with Macrium Reflect. That gave an option to open a Command Prompt, from which I tried to run sfc again, using the offboot and offwin string. However, I am getting a 'WRP could not start the service' or 'system repair pending' message. I assume the 'system repair' means the looping update, as i am not aware of anything else.
This really is a very frustrating situation.

Many times when sfc /scannow is malfunctioning or finds corruption that it cannot fix the DISM commands can fix OS corruption.

Open administrative command prompt and type or copy and paste:
1) dism /online /cleanup-image /scanhealth
2) dism /online /cleanup-image /restorehealth
3) sfc /scannow
4) chkdsk /scan
5) When these have completed > right click on the top bar or title bar of the administrative command prompt box > left click on edit then select all > right click on the top bar again > left click on edit then copy > paste into the thread

This is a link on the multiple DISM commands to repair a Windows image:
Use DISM to Repair Windows 10 Image Windows 10 Tutorials


If there are problems where neither scannow nor restorehealth fix underlying OS problems the next step that can fix both is an in place upgrade repair:

This is a link on the in place upgrade repair:
Repair Install Windows 10 with an In-place Upgrade Windows 10 Tutorials

I can report that my problem (installing updates properly) started after the Creators update. Throughout all of this my machine has and still does run very well indeed. My only outstanding issue is that of a correct and full installation of KB4048955 which shows as installed in the "uninstall updates" list, but which will always try to install again when I allow updates to run. The loop is continuous, slowing down my system as it never stops using my resources.
Here is the report from DISM, SFC and CHKDSK. I will try the scans suggested by dalchina shortly.
Many thanks for your continued help.

(c) 2017 Microsoft Corporation. All rights reserved.

C:\WINDOWS\system32>dism /online /cleanup-image /scanhealth

Deployment Image Servicing and Management tool
Version: 10.0.16299.15

Image Version: 10.0.16299.64

[======= 12.8% ]
Error: 605

The specified buffer contains ill-formed data.

The DISM log file can be found at C:\WINDOWS\Logs\DISM\dism.log

C:\WINDOWS\system32>dism /online /cleanup-image /restorehealth

Deployment Image Servicing and Management tool
Version: 10.0.16299.15

Image Version: 10.0.16299.64

[===== 9.9% ]
Error: 605

The specified buffer contains ill-formed data.

The DISM log file can be found at C:\WINDOWS\Logs\DISM\dism.log

C:\WINDOWS\system32>sfc /scannow

Beginning system scan. This process will take some time.

Beginning verification phase of system scan.
Verification 13% complete.

Windows Resource Protection could not perform the requested operation.

C:\WINDOWS\system32>chkdsk /scan
The type of the file system is NTFS.
Volume label is OS.

Stage 1: Examining basic file system structure ...
413440 file records processed.
File verification completed.
11706 large file records processed.
0 bad file records processed.

Stage 2: Examining file name linkage ...
15778 reparse records processed.
499752 index entries processed.
Index verification completed.
0 unindexed files scanned.
0 unindexed files recovered to lost and found.
15778 reparse records processed.

Stage 3: Examining security descriptors ...
Security descriptor verification completed.
43157 data files processed.
CHKDSK is verifying Usn Journal...
37946336 USN bytes processed.
Usn Journal verification completed.

Windows has scanned the file system and found no problems.
No further action is required.

89432039 KB total disk space.
46389796 KB in 168806 files.
123464 KB in 43158 indexes.
0 KB in bad sectors.
526383 KB in use by the system.
65536 KB occupied by the log file.
42392396 KB available on disk.

4096 bytes in each allocation unit.
22358009 total allocation units on disk.
10598099 allocation units available on disk.

C:\WINDOWS\system32>

I have installed Disk Sentinal. Here is what appears to be a perfect report.

Grateful thanks to all who contributed to resolving my update problem. The in-place upgrade from an iso file did the trick and although the procedure took a long time, it was of course worth every minute. I am now fully updated and my system is running very well.
Thanks again and kind regards.