Notebook Operating System and Recovery

Here goes with my next problem:

Since I recently completed a fresh install of Windows 10 64bit on my dv7, I have been receiving CONSTANT - and I mean every few seconds! - notifications that:

"You are running out of disk space on Recovery Drive (D:) Click here to see if you can free some space."

Clicking on the notification provides no mechanisms to remove disk content, showing 0 bytes available to remove.

Looking at Drive 😧 Properties, the (presumably a partition) has a capacity of 25GB with 1.89MB free space .... so there is clearly a problem.

Looking at Drive 😧 contents, there are only two folders. One is labelled Recovery (containing 366,000KB) and the other Windows10Upgrade (containing 3,072,512KB). I am assuming that there are files or folders that I am unable to see, despite setting View: Hidden Items in File Manager.

The Windows 10Upgrade folder is dated to coincide with my recent fresh install of Windows 10 and therefore, is likely to allow me to recover my last copy of Windows 10. Presumably, now that I have been running my fresh installation for nearly a month, can be deleted.

I assume that the Recovery folder is likely to be my original Windows 8 Recovery copy which I was exhorted to keep by HP under pain of being unabe to recover the machine if that was deleted.

I doubt very much that I shall ever go back to Windows 8 or 8.1 since despite the several apparent incompatibilities of HP hardware with Windows 10, I prefer the OS and I prefer the security offered by keeping fully up to date. 

Can one of you clever folks who know about this stuff please advise me what I really HAVE to keep and what I can safely delete?

Many thanks,

JLBH1