Hard drive problem, and can't access externally - what to do?

OK, I'm having a hard drive problem I've never encountered before and... well, I haven't been very diligent on my backups (it has been 6 months), so I'm very worried I may lose some valuable files. I'm hoping someone here can help me.

BACKGROUND: I have an HP dv6 laptop computer running Windows 7 that was working fine for a couple of years. Then, all of the sudden without any warning, I started to experience a peculiar hard drive behavior. Upon launching a program (3rd party or Microsoft), the hard drive would become completely busy, causing the whole system to be sluggish and apps to not respond. The drive would make a series of clicks and access sounds in a certain pattern that repeats every 2~3 seconds. Same exact pattern, over and over. Then after a while, it would subside. Yet, it would repeat again and last longer. I was able to run diagnostics on my drive and everything checked out. I even booted up in a special HP BIOS diagnostic where it could check the hard drive -- no errors found. I ran Malware Bytes, but it turned up nothing significant. I booted up in SAFE mode, still same problem. I posted about it, but couldn't get any advice that helped.

OK, I figured there must be a bad driver somewhere that was caused by a Windows update, so I decided to roll back to an earlier checkpoint. Well... BAD MOVE. The rollback worked, but it made things worse. Now I was getting this hard disk access loop DURING BOOT UP, which didn't happen before. Well, that right there informed me that this is a hard disk issue.

Now, if I do boot up there is a short period of time after the desktop initializes where I can launch Windows Explorer and see folders/files. I can even copy some files from C drive to D drive. So the drive seems OK to a degree.

MY PROBLEM: I take the drive out and mount it on a USB 3.0 SATA III adapter, attached to my Windows 8 computer. However, it does not see the partitions as something readable. It comes up with 3 partitions and sees them as RAW. I cannot get permissions.

So I'm perplexed... The only thing I can think of is that maybe my hard drive is encrypted? Is there any way I can check? This is not a work laptop. It is personal. And I don't recall setting up any encryption on it.

MY OTHER PROBLEM: OK, I can boot up into Safe Mode command prompt... and from there I'm able to copy files to a USB drive, in between these long drive accesses (it still happens). However, it won't recognize my 16Gb USB drive. I can only use my 2Gb one. While I was able to pull off a few important smaller documents, I have some video media that I *really* want to rescue. I can't do it with a tiny USB drive. Is there some other mode I can possibly try? Is there any way to get a multi terabyte external drive to be recognized in this mode?

Thankfully I have been able to slowly but gradually pull off files that I really needed, now fiddling around getting other files that I'd like to have. The highest USB drive I could get recognized is 8Gb. So at least I was able to pull over around 7Gb of files with each swap. Still mystified why my 16Gb USB drive won't work. Anyway, it was clumsy having to use XCOPY... so I launched Explorer and was able to get the GUI interface going. The hard drive loop kicked in once or twice, but then subsided. The only strange thing is that the click+drag functionality would stop working after each drag... so I'd have to close the window and open a new one.

I'm still perplexed... as to why I could not access the drive externally, that it was seen as raw devices. There must be some kind of drive encryption. If a known encryption is used, is there some method by which the drive can be used externally? Or is it permanently relegated to internal use until decrypted?

Hi Jumanji, thanks for your reply. Yes, I had installed the HDD back into the laptop. I'm able to boot up, log in, and the desktop initializes. Then that pesky busy hard drive happens. What is strange is that in the Resource Monitor, I can watch the disk activity and while the hard drive activity loop is happening, I see a hard drive graph that shows a mostly idle drive. Some blips of activity. For instance, when I click to launch Windows Explorer, I see a spike and then a drop off. The display alternates between 100 KB/sec and 1 KB/sec. But in either view, it doesn't show a very busy hard drive. YET... the drive light is fully on, and that repetition of hard drive activity sounds continues. CPU usage is practically 0... but launching and trying to use Windows Explorer is painfully slow.

The symptom to me feels like some kind of compromise to core software that is involved with hard drive usage. Something is impeding it for periods of time. And I don't see how this could be malware, as I ran malware bytes and nothing turned up... then later when I booted after restoring to an earlier restore point, it started happening in the early phase of booting up, before any non system applications could be actively running.

Thanks for your suggestion on the Linux USB boot... but I'm not confident that will work... if Windows sees the Windows formatted drive as raw when mounted as an external drive, I'm not confident Linux will do any better. The main thing is that I am able to get data, albeit slowly, by mounting a USB drive and copying files over.

What puzzles me the most is this: If this hard drive behavior is indicative of a failure, does that mean a firmware failure of some kind where the magnetic media is OK? I mean... I'm able to copy all of these files and don't get any errors. Also, just to clarify, the laptop had not been subjected to any physical trauma. Everything was working fine and then... this problem started seemingly out of nowhere, not connected to any event.

To me it looks like your OS has become cranky and is responsible for all your problems. If you try Linux and if everything works fine we can come to that conclusion. If you want to keep beating on your own thinking without trying Linux, I have nothing to say. It is upto you. Keep repeating the same thing. You will be taken nowhere.

Note: If with Linux also you experience the same problem like 8GB flash drive looking like a 2GB drive then I would suspect a motherboard hardware fault. You can't draw any conclusion by putting your drive in an external enclosure and on a Windows 8.1. You are putting extraneous elements on an extraneous machine and trying to link it with your machine No.1 (your laptop) without trouble shooting your HP laptop and the OS in it.