Windows 8.1 on an iMac

Question

I am trying to install Windows 8.1, via Bootcamp on my 21.5", late 2014 iMac.  I have the flash drive set ok, and Bootcamp creates the partition. The computer restarts, the Windows installer starts the install process.  Up to this point all is well. 
When the installer asks where to install I select the bootcamp partition, but the installer says  
" Windows can not be installed to this hard drive space.  Windows must be installed to a partition formatted as NTSF
Disk utility tells me the file format  is NTSF and it was created by BootCamp.  When I use the Windows installer to format the partition, I get the message "We couldn't create a new partition or locate an existing one.  For more info, see the setup log files"
Not sure why this is getting stuck.  I've tried several times with the same result.

Answer 1

COMMAND 1
/dev/disk0
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                 *1.0 TB     disk0
   1:      EFI EFI                                         209.7 MB   disk0s1
   2:      Apple_HFS NewMac 2014           957.0 GB   disk0s2
   3:      Apple_Boot Recovery HD             650.0 MB   disk0s3
   4:      Microsoft Basic Data                       42.3 GB    disk0s4
COMMAND 2
No CoreStorage logical volume groups found
COMMAND 3
gpt show: /dev/disk0: mediasize=1000204886016; sectorsize=512; blocks=1953525168
gpt show: /dev/disk0: PMBR at sector 0
gpt show: /dev/disk0: Pri GPT at sector 1
gpt show: /dev/disk0: Sec GPT at sector 1953525167
       start        size  index  contents
           0           1         PMBR
           1           1         Pri GPT header
           2          32         Pri GPT table
          34           6        
          40      409600      1  GPT part - C12A7328-F81F-11D2-BA4B-00A0C93EC93B
      409640  1869140608      2  GPT part - 48465300-0000-11AA-AA11-00306543ECAC
  1869550248     1269536      3  GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC
  1870819784        1592        
  1870821376    82702336      4  GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7
  1953523712        1423        
  1953525135          32         Sec GPT table
  1953525167           1         Sec GPT header
COMMAND 4
Disk: /dev/disk0    geometry: 121601/255/63 [1953525168 sectors]
Signature: 0xAA55
         Starting       Ending
#: id  cyl  hd sec -  cyl  hd sec [     start -       size]
1: EE 1023 254  63 - 1023 254  63 [         1 - 1953525167] <Unknown ID>
2: 00    0   0   0 -    0   0   0 [         0 -          0] unused     
3: 00    0   0   0 -    0   0   0 [         0 -          0] unused     
4: 00    0   0   0 -    0   0   0 [         0 -          0] unused