Confirm that you've created a full restore disk. It could be simply a repair/boot disk. I recently created restore disks from my laptop (and I know they works as I've used them) and they came to 3 DVDs.
With a Windows full restore disk set you'll completely overwrite the HDD (wiping your Arch install), reinstating your Windows and OEM partitions. That laptop will be as it was when you bought it. Although you may get other options when you boot the DVDs remember that Windows is quite greedy when it comes to installing/repairing and doesn't generally grasp the concept that there may be other OSes installed. In fact, it won't understand your XFS/BTRFS/Ext4/LVM etc partition and simply overwrite it.
So to answer your question - yes you can delete the OEM partition as long as you check that your restore disks are complete beforehand, but you won't be able to restore the OEM partition or Windows without overwriting your Arch install.
As well as the answer by @schaiba you can use a separate
home directory if you triple (or even quadruple) boot. If you point each distro to the same
home directory and keep all your settings, emails between distros.