BSOD W7 Unmountable Boot Volume (tried everything I can think of)

Hi guys, new here.

I'm an amateur(ish) PC/Laptop repairer and I rarely get stuck but this one has stumped me good and proper. Got a Tosh Satellite L670-1DR here stuck in a boot loop. Running W7. I selected disable reboot upon failure so I could see the BSOD and it's the UNMOUNTABLE_BOOT_VOLUME one. I've seen this before but have always managed to get around it.

Won't boot to safe mode
Won't boot to normal
Boot to safe mode with command prompt just does the same thing
Recovery option goes nowhere (just black screen with arrow)
Booting from W7 disk (genuine) produces same result, doesn't go anywhere (as above)
HDD is present in BIOS

I can't get to a CMD prompt to run anything like chkdsk (unless I'm missing something?)

Any ideas?! Bit perplexed!

BTW I have read just about every similar thread but all of them are relying on being able to get to the recovery options.

Hi! Yeah it's set to boot from DVD drive first, and it does do this (press any key etc...) but it goes nowhere from there. I left it over an hour and still only get the black screen with arrow.

I haven't tried taking the battery out yet because I hadn't thought of it, I'll give it a whirl! That fixes the very occasional blank screen problem on my own Tosh so worth a stab.

I think I have a few SSD's knocking around here somewhere which I could whack in but they have no OS on them. I'm leaning towards the most knackered HDD I've been presented with so far. Normally I can wriggle my way around a boot problem, backup whatever pointless crap the owner "needs" and then just go from there but I can't get this one to do a damn thing!

I could create one (I only have W10 on USB right now) but if it won't boot from CD/DVD I'm not sure why it would start behaving with boot from USB. I'll try it but I'm doubtful :/

I think the HDD is toast, but it's the most burnt toast I've had in my own experience!

I've had great luck with HDDRegenerator if is an HDD issue. otherwise, EasyRE has fixed boot/MBR errors.

you can take one stick of memory out at a time and see if a bad stick.

strange it will not boot to a CD? pretty much need to boot from CD or USB at this point?

Thanks for the tips guys. Ordinarily I would also suspect RAM issue but the fact it boots to BSOD Unmountable Boot Volume put me off that idea. It's definitely worth a throw though so I'll have it apart now! It would be nice if I could get to a command prompt but can't seem to get there no matter how I try.

It absolutely will not boot from CD, it tries but it just leads to a blank screen with the arrow, I've left it for ages and it doesn't make any progress so I can't even use the repair tools. F8 repair option does the same thing. It's a bit of a head scratcher!