Removing Acronis tib from ESP partition

Hello,

I'm trying to upgrade to Win 10 from Win 8.1
It can't upgrade as the boot sector partition is full. When I view the partition with a partition tool it shows the partition is occupied by an Acronis tib backup file.
I can't do anything with the partition as it's locked and won't allow me to delete any contents or expand the partition.
I've attached the partition and disk info.

Can anyone advise?

Thanks

Paul