So, I bought my HP Notebook 15 2 years back with Windows 8.1 installed. It came with a factory reset recovery partition. Last year, in the July of 2015, I updated to Windows 10, free of charge, as my software and hardware were compatible. But, long story short, I had to use this recovery partition, and it, as I expected, restored back to Windows 8.1. So I had to go through the upgrade process again. So, more to the point, I would like to know if it would be possible to format my current recover partition, and use it as a USB flash drive, and create a recover drive on that, and how.
It is safe to format/delete an OEM recovery partition (which holds recovery tools from, say Lenovo or Dell) as long as you don't want any of it's offering.
But it is not recommended to delete/modify Windows recovery partition (and other reserved partitions), which are created during a fresh install of Windows onto a blank drive.
Also, whatever you do it's really unlikely you can have a HDD partition show up as removable USB drive. Even if you achieve so with sophisticated methods it's unlikely you can boot from it and install Windows without having drawbacks.
I would suggest creating a bootable USB with tools like Rufus or simply burn the DVD for beginners.
Please do not take offense, I do not mean it. The question was "is it safe" and safety is relative.
Given your level of experience and confidence a safe way would be to leave partition as is, buy a USB drive, "play" with it (create recovery disk, restore from it). When you have tested the restore process, only then you can delete current partition and try to replace it with Windows 10.
If you started with deleting current recovery partition and something goes wrong, then you are left with no other option but getting physical installation media. Hence it is not safe in your particular case.
You can safely format the recovery partition once upgraded to Windows 10. You can do this from
Control Panel > Administrative Tools > Computer Management > Disk Manager
Then you can use it as a separate disk for storing files and not be troubled with going back to 8.1.
But if C: drive and that partition are actually on one single drive then Windows won't allow you to create recovery partition.
Consider if your disk crashes. You would lose both recovery and the main C: drive. What's the point in creating recovery? It's like making backups of a project in the same file, so if the file gets destroyed, so are the backups destroyed as well.
If you have blank rewritable CDs or DVDs then you can create recovery boot disk there if you have no empty pendrives to spare.