Can I expand Win 11 UEFI C:\ drive partition?

I've updated my PC to Win 11 Pro. My Macrium Reflect backup ran this morning but errored out saying I had an invalid partition. Checking disk management, I see there are 4 additional partitions on my C:\ drive (see attached) that weren't there before the upgrade.

Now that this drive is UEFI, can I delete those partitions and expand the actual C:\ partition? I'm not familiar with all the UEFI restrictions.

I misread your question and had to edit my response. No you cannot delete the "extra" partitions. the 100mb partition is required to boot your OS

You can delete the recovery paritions and move the EFI partition over with a tool and reclaim about 2gb of storage. But you will lose the spare recovery partition (wont be able to get in recovery if the C:\ partition is inaccessible)

Was the Macrium error produced specific?

Are you just running an old backup.xml file that you haven't updated for your new disk layout yet? You likely need to create a new one if Win11 upgraded your disk layout during migration. I didnt know they were doing this, i guess mbr2gpt is being used?

It said partition 1 (the 658mb partition) was invalid. I would like to end up with only 2 partitions instead of 5 as I will never use those other partitions and, therefore, they are a waste.

The 658mb par is #2

Par #1 is your Windows partition

Also keep in mind... removing the recovery partitions will not stop Windows from "booting/working" but may affect Windows Updates in the future (Not sure about this, when it tries to update them for future major version upgrades).

I used the mbr2gpt utility to change the C:\ drive so I could update to Win 11. After seeing the error (that was the only description Macrium gave) I edited the xml file to specify only the C:\ partition and ran the backup again to successful completion. The extra partitions are:

658mb (healthy, recovery partition)
100mb (healthy, EFI system partition)
547mb (healthy, recovery partition)
865mb (unallocated)

Why 3 recovery partitions? Can I delete the unallocated partition and just expand the C:\ drive partition to use those 865mb?

The Unallocated partition is already deleted and empty unused space. Thats what unallocated means.
Any partitions you delete will become part of that unallocated pool.

IDK why there are 2 recovery partitions, from the redacted names I am guessing you have a multiboot setup. Is it possible one of them is for another Windows installation you have that points to that disk for its recovery partition? Again if I am correct in that assumption it may be ok to remove the real recovery partition now without noticing any issues but during one of the fall/spring updates Windows Update may fail you if the partition isn't present to update along with the system, only time will tell how Win11 behaves.

You can assign letters to those partitions by right clicking them in disk managment and see what they contain (check file version #'s etc to see which installation they are for). There are several ways to check where they came from, or what points to them.

Whoops, sorry to mislead you. The redacted drives are just other separate HDD/SSD drives in my PC. I'd just like to add the un-needed disk space back to the Windows partition if I could. I won't be using the 865mb for anything else.

You will need a 3rd party tool. And you should run "reagentc /disable" from an admin cmd prompt in the live OS before removing the recovery partitions. (Noted here: Cloning System Partition, Recreating EFI and Recovery partitions...)

For the tool to move the EFI partition to the end of the disk, I would recommend either Ease US partition master or MiniTool Partition Wizard.

Otherwise you can completely delete and recreate it, but you need the recovery environment to do that. Or install disk.

Great!! Thank you for your time and effort.