Hi Ramesh, thanks that makes sense :) I don't know whether I should be starting a new post for my particular problem or not ... but I have been doing some more digging using your posts above, and will list what I have found here:
On my desktop PC, when I used "open with" for a .jpg file and selected "Microsoft WinRT Storage API" then originally it would open the ClipChamp app. (Which I have since uninstalled).
I tried using ProcMon as mentioned above (Process Monitor) and found the following section which I'm guessing is when it tries to actually open the file, and there are multiple references to this app identifier: AppXvsqkg1th80rv6s2rkh5m1hjp3hxryydd (presumably the app it tries to use.)
17:02:39.1883727 Explorer.EXE 15136 RegQueryValue HKCR\Applications\zipfldr.dll\NoOpenWith BUFFER OVERFLOW Length: 12
17:02:39.1883955 Explorer.EXE 15136 RegCloseKey HKCR\Applications\zipfldr.dll SUCCESS
17:02:39.1884132 Explorer.EXE 15136 RegEnumKey HKCR\Applications NO MORE ENTRIES Index: 86, Length: 288
17:02:39.1884293 Explorer.EXE 15136 RegCloseKey HKCR\Applications SUCCESS
17:02:39.1884450 Explorer.EXE 15136 RegCloseKey HKCU\Software\Classes\Applications SUCCESS
17:02:39.1884681 Explorer.EXE 15136 RegCloseKey HKCU\Software\Classes\Local Settings\Software\Microsoft\Windows\CurrentVersion\AppModel\Launcher\Activation\UWARegAssociationInteropProgId SUCCESS
17:02:39.1885030 Explorer.EXE 15136 RegCloseKey HKCU\Software\Classes\AppXcesbfs704v2mjbts9dkr42s9vmrhxbkj SUCCESS
17:02:39.1885203 Explorer.EXE 15136 RegCloseKey HKCU\Software\Classes\AppX43hnxtbyyps62jhe9sqpdzxn1790zetc SUCCESS
17:02:39.1885366 Explorer.EXE 15136 RegCloseKey HKCU\Software\Classes\AppX2jm25qtmp2qxstv333wv5mne3k5bf4bm SUCCESS
17:02:39.1885555 Explorer.EXE 15136 RegCloseKey HKCU\Software\Classes\AppXvsqkg1th80rv6s2rkh5m1hjp3hxryydd SUCCESS
17:02:39.1885714 Explorer.EXE 15136 RegCloseKey HKCU\Software\Classes\AppXkv2jqn1pq8ajm0p5dhgqde7aafykkrrn SUCCESS
17:02:39.1886006 Explorer.EXE 15136 RegCloseKey HKCR\Applications\Acrobat.exe SUCCESS
17:02:39.1886182 Explorer.EXE 15136 RegCloseKey HKCU\Software\Classes\Applications\Code.exe SUCCESS
17:02:39.1886354 Explorer.EXE 15136 RegCloseKey HKCR\Applications\Photoshop.exe SUCCESS
17:02:39.1886524 Explorer.EXE 15136 RegCloseKey HKCR\Applications\VSLauncher.exe SUCCESS
17:02:39.1886691 Explorer.EXE 15136 RegCloseKey HKCR\Applications\WINWORD.EXE SUCCESS
17:02:39.1886899 Explorer.EXE 15136 RegCloseKey HKCR\Applications\wmplayer.exe SUCCESS
17:02:39.1887097 Explorer.EXE 15136 RegCloseKey HKCR\Applications\wordpad.exe SUCCESS
17:02:39.1887348 Explorer.EXE 15136 RegCloseKey HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.jpg\OpenWithList SUCCESS
17:02:39.1887581 Explorer.EXE 15136 RegCloseKey HKCU\Software\RegisteredApplications SUCCESS
17:02:39.1887792 Explorer.EXE 15136 RegCloseKey HKLM\SOFTWARE\RegisteredApplications SUCCESS
17:02:39.1887992 Explorer.EXE 15136 RegQueryKey HKCU\Software\Classes\AppXvsqkg1th80rv6s2rkh5m1hjp3hxryydd SUCCESS Query: Name
17:02:39.1888160 Explorer.EXE 15136 RegQueryKey HKCU\Software\Classes\AppXvsqkg1th80rv6s2rkh5m1hjp3hxryydd SUCCESS Query: HandleTags, HandleTags: 0x0
17:02:39.1888322 Explorer.EXE 15136 RegOpenKey HKCR\AppXvsqkg1th80rv6s2rkh5m1hjp3hxryydd NAME NOT FOUND Desired Access: Maximum Allowed
17:02:39.1888501 Explorer.EXE 15136 RegQueryValue HKCU\Software\Classes\AppXvsqkg1th80rv6s2rkh5m1hjp3hxryydd\AppUserModelID NAME NOT FOUND Length: 144
17:02:39.1888652 Explorer.EXE 15136 RegQueryKey HKCU\Software\Classes\AppXvsqkg1th80rv6s2rkh5m1hjp3hxryydd SUCCESS Query: Name
17:02:39.1888808 Explorer.EXE 15136 RegQueryKey HKCU\Software\Classes\AppXvsqkg1th80rv6s2rkh5m1hjp3hxryydd SUCCESS Query: HandleTags, HandleTags: 0x0
17:02:39.1889028 Explorer.EXE 15136 RegQueryKey HKCU\Software\Classes\AppXvsqkg1th80rv6s2rkh5m1hjp3hxryydd SUCCESS Query: HandleTags, HandleTags: 0x0
17:02:39.1889201 Explorer.EXE 15136 RegOpenKey HKCU\Software\Classes\AppXvsqkg1th80rv6s2rkh5m1hjp3hxryydd\Application SUCCESS Desired Access: Query Value
17:02:39.1889380 Explorer.EXE 15136 RegQueryKey HKCU\Software\Classes\AppXvsqkg1th80rv6s2rkh5m1hjp3hxryydd\Application SUCCESS Query: Name
17:02:39.1889533 Explorer.EXE 15136 RegQueryKey HKCU\Software\Classes\AppXvsqkg1th80rv6s2rkh5m1hjp3hxryydd\Application SUCCESS Query: HandleTags, HandleTags: 0x0
17:02:39.1889713 Explorer.EXE 15136 RegOpenKey HKCR\AppXvsqkg1th80rv6s2rkh5m1hjp3hxryydd\Application NAME NOT FOUND Desired Access: Maximum Allowed
17:02:39.1889915 Explorer.EXE 15136 RegQueryValue HKCU\Software\Classes\AppXvsqkg1th80rv6s2rkh5m1hjp3hxryydd\Application\AppUserModelID SUCCESS Type: REG_SZ, Length: 76, Data: Clipchamp.Clipchamp_yxz26nhyzhsrt!App
17:02:39.1890090 Explorer.EXE 15136 RegCloseKey HKCU\Software\Classes\AppXvsqkg1th80rv6s2rkh5m1hjp3hxryydd\Application SUCCESS
17:02:39.1891080 Explorer.EXE 15136 RegQueryKey HKLM SUCCESS Query: HandleTags, HandleTags: 0x0
17:02:39.1891234 Explorer.EXE 15136 RegOpenKey HKLM\Software\Microsoft\Windows\CurrentVersion\Explorer\SyncRootManager SUCCESS Desired Access: Read
17:02:39.1891431 Explorer.EXE 15136 RegSetInfoKey HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\SyncRootManager SUCCESS KeySetInformationClass: KeySetHandleTagsInformation, Length: 0
17:02:39.1891563 Explorer.EXE 15136 RegQueryKey HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\SyncRootManager SUCCESS Query: Cached, SubKeys: 1, Values: 0
17:02:39.1891721 Explorer.EXE 15136 RegCloseKey HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\SyncRootManager SUCCESS
17:02:39.1893731 Explorer.EXE 15136 CreateFile C:\Users\medmo\Desktop SUCCESS Desired Access: Read Data/List Directory, Read Attributes, Synchronize, Disposition: Open, Options: Synchronous IO Non-Alert, Attributes: n/a, ShareMode: Read, Write, Delete, AllocationSize: n/a, OpenResult: Opened
17:02:39.1894191 Explorer.EXE 15136 QueryRemoteProtocolInformation C:\Users\medmo\Desktop INVALID PARAMETER
17:02:39.1894564 Explorer.EXE 15136 QueryDirectory C:\Users\medmo\Desktop\c.jpg SUCCESS FileInformationClass: FileIdBothDirectoryInformation, Filter: c.jpg, 2: c.jpg
17:02:39.1895000 Explorer.EXE 15136 CloseFile C:\Users\medmo\Desktop SUCCESS
17:02:39.1895594 Explorer.EXE 15136 RegQueryKey HKCU\Software\Classes\AppXvsqkg1th80rv6s2rkh5m1hjp3hxryydd\Shell\open SUCCESS Query: Name
17:02:39.1895767 Explorer.EXE 15136 RegQueryKey HKCU\Software\Classes\AppXvsqkg1th80rv6s2rkh5m1hjp3hxryydd\Shell\open SUCCESS Query: HandleTags, HandleTags: 0x0
17:02:39.1895961 Explorer.EXE 15136 RegOpenKey HKCR\AppXvsqkg1th80rv6s2rkh5m1hjp3hxryydd\Shell\open NAME NOT FOUND Desired Access: Maximum Allowed
Checking the registry editor for that app id it does seem to match ClipChamp (which isn't installed).

And searching for the id elsewhere in the registry it shows up for multiple audio visual file formats in their "OpenWithProgids" section.

I checked the "open with" right click menu for a few of those file types in Windows Explorer and they do all show the same broken menu item of "Microsoft WinRT Storage API". (E.g. .png, .mov, .mkv)

If I delete that app id from the .jpg OpenWithProgIds section (Computer\HKEY_CLASSES_ROOT.jpg\OpenWithProgids) then it does remove "Microsoft WinRT Storage API" from the "Open With" right click menu - which is nice :) But I don't know if doing this is a bad idea? I'm tempted to go through all the different file types and remove it from all of them in the registry. But maybe there is a better way of doing this! And if I reinstall ClipChamp then maybe they would all come back again. (Advice on whether it's ok for me to manually delete them all would be appreciated!)
