Booting Windows 8.1, blinking underscore problem - with data already on partition.

Question

So I updated my OS X software from the App Store (just a newer version of Yosemite than before) not too long ago.  I wanted to boot into windows because I had certain data and applications on there I needed that have no version for Mac.  So I tried booting, but when I boot the windows partition, nothing goes beyond the blinking underscore.  I tried researching the problem; people have had the issue with the blinking underscore, but that is when they tried installing windows [there was no data on the line].  I however installed windows quite a while back and it is stacked with data that is pretty important for me.  If there was a way for me to transfer the data to an external drive or the Mac partition as backup, I'd gladly just re-install windows.  But there's data, I need the data on that partition.  I know it's 100% possible to get the data, but I'm not sure anyone has found a way yet[?].  I've seen solutions that require things like gdisk, but the problem where that stuff would be required is a little different from mine; their partition wouldn't show as being bootable at all, so I didn't try that method (I'm just being cautious, Macs aren't my specialty ) However, in Disk Utility, the partition is labeled as disk0s4, which is similar to those other problems people have had in the past.  If possible, can somebody point me in the right direction, or maybe even walk me through it?  I'd greatly appreciate it.  And if my problem does get solved, can someone suggest a safe way of updating OS X without it corrupting my data on other partitions?

Answer 1

Well the only update other than Yosemite would be Autodesk Sketchbook from the app store, but I doubt that it would have to do with bootcamp, so no, there were no updates other than a new version of Yosemite.  And have testdisk, but do I need to search for lost partitions?  That's an option I can see here. If I need to look specifically for NTFS headers, then maybe I'd needs steps on how to do that.
EDIT: I started running the process to look for lost partitions, and these are the first things that came up:
0 D HPFS - NTFS           2292342621 2292363587      20967
  HPFS - NTFS           2292342621 2292363587      20967
check_FAT: can't read FAT boot sector
Invalid FAT boot sector
0 D FAT32                 3674955484 3685476902   10521419
  FAT32                 3674955484 3685476902   10521419
check_FAT: can't read FAT boot sector
Invalid FAT boot sector
0 D FAT32                 2842018750 6075856388 3233837639
  FAT32                 2842018750 6075856388 3233837639
Invalid NTFS or EXFAT boot
0 D HPFS - NTFS            987918603 1334613816  346695214
  HPFS - NTFS            987918603 1334613816  346695214
  HFS                   1334727563 1408127882   73400320
  Stop
Is this what TestDisk is supposed to be trying to find anyways?
EDIT 2:  It stopped and showed me this message.  My total hard drive space is 750 GB including all partitions.  I honestly have no Idea why the 4000 and 3000 GB are showing up
Disk /dev/disk0 - 750 GB / 698 GiB - 1465149168 sectors (RO)
The harddisk (750 GB / 698 GiB) seems too small! (< 4144 GB / 3860 GiB)
Check the harddisk size: HD jumpers settings, BIOS detection...
The following partitions can't be recovered:
     Partition               Start        End    Size in sectors
>  FAT12                  962821072 2746820174 1783999103
   FAT32                 1249202674 1683653752  434451079
   HPFS - NTFS           1465147384 2692806640 1227659257
   HPFS - NTFS           1465147391 2692806647 1227659257
   HFS                   1465149124 1466418659    1269536
   FAT16 LBA             1789599502 6051012398 4261412897
   HPFS - NTFS           1839250623 4694089744 2854839122
   FAT16 <32M            2086827920 2365890772  279062853
   HPFS - NTFS           2290244103 2290265101      20999
   HPFS - NTFS           2292342621 2292363587      20967
[ Continue ]
913 GB / 850 GiB