How to delete an extended disk parition without windows installed?

So I tried upgrading to a clean install of Windows 10 today, and with my primary hard drive being 3 TB I had been using an extended partition, and now whatever I do I cannot seem to erase or create new partitions through the windows installer or even DiskPart. the "clean" command appears to work, but when I try creating a single partition in windows setup it goes back to the old 2 TB/700 GB split, and refuses to install on either partition. I tried creating an Acronis boot disk through another computer in order to erase the partition, but it keeps saying it needs Windows to launch. So I'm in a bit of a catch 22 here, any help would be appreciated.