have just shrunk the size of the c partition and created a partiotion for a d drive to see what impact it has. In summary :-
- Disk management and explorer show the C partition as 450.34 GB
-...

results from chkdsk are all good :-

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

497815551 KB total disk space.
39229304 KB in 113861 files.
...

Have just performed a clean install including wiping the drive. Sadly no change.

Here are a few images that capture the problem after the fresh install

Disk Manager showing 512gb drive and...

good thought but the drive is not compressed. Not sure it will make any difference but going to compress and then uncompress to see if it will nudge the system to correct the storage size.

many thanks for the suggestions. I have looked through and sadly none help. I have even does a fresh windows install (keeping data).

Searches for the problem show many hits but most are where...

looking at the two suggestions sadly does not solve the problem :-

"there is a possible answer at the end
https://answers.microsoft.com/en-us/...a3aa843?page=2" is about finding and removing a...

Running Windows 10 Home 20H2 (Build 19042.964) on an AMD based Windows Surface Laptop 4 with 512GB SSD.

Even though it has a 512GB SDD as confirmed by both disk management and file explorer,...