Try using Windows file manager... I think you right click to view/change properties
If that doesn't work, I don't know
Seems to be write protected
There is also the possibility (as you have not quoted any error message) that the Catalog file is 'Locked' by Lightroom. Happens any time a computer crashes with Lightroom running!
I refer you to this help page for this possibility-
I have restored the LRCAT file and the preview file from a backup and now it works! Thanks for your help. Best regards, Guy