Windows 7 OS won't load

Have HP Pavilliion P6000 Series desktop with Windows 7 Home Premium 64-bit. When I turn on computer, it gets to the Windows logo, stays a while, screen goes black and then tries to reboot; the same process starts again. Here is what I've tried:

1. Tried system restore, but all my restore points have vanished. (I generally create at least 1 restore point a week.)
2. Tried repair tools, but couldn't repair anything; said "unusual configuration" is the root cause or words to that effect.
3. Tried using system repair disk, but still didn't work.
4. Ran chkdsk and noticed that all data was in the D drive where my OS is stored. Would that effect my Windows OS booting. Am puzzled as to how that happened.
5. Tried to back up data to external drive, saw the drive listed for selection and highlighted, but then got the message that the drive didn't have enough empty space. The external drive has 465G empty and only needed 365G to back up all data. Didn't matter if I only tried to back up 21 G.
6. I have system image, albeit a year old, but I'm wondering if that will even work and hesitant to lose irreplaceable data.

Should I try:

1. My OS is in the D drive. Can I try booting from a Windows 7 Professional 32-bit with SP1 installation disk or would compatibility be an issue since my computer is 64-bit?
2. Removing my hard drive and putting in an enclosure to connect to another computer. Would moving data from D drive to another drive help?

Suggestions, please. Not afraid to try things if given clear directions. Thanks

One solution I found useful, if you're willing to try, is to install a Linux distribution, such as Antergos, on any available space (a small 20GB logical partition will do just fine). When you do this, Antergos will recognize the presence of most other operating systems, including Windows, and present you with a list to choose from. Once that happens, you can usually boot into Windows, and never use the Linux distro - it will be there only to provide GRUB2 bootloader. It worked for me, but your Windows system files must be uncorrupted, of course.

If you want to get a little fancy, you could install Grub Customizer inside Antergos - that will allow you to easily modify the OS list. But that's not necessary. Good luck.

You should backup your data first (perhaps first link is better for you at this stage):
Emergency Kit - save your files from a dead OS
Copy & Paste - in Windows Recovery Console