Yes, you can. The laptop has already been register with 10.

Only way you can't go back to 10 for free on a PC/Laptop that has already had 10 on it is if you change motherboards. Hence the MS rule that 10 is free on that PC for the life of the PC (motherboard).

Hard drives can be changed out, no problem.

Yes, again, you can put 10 on it, and it will activate.

That's cool, Paul. I didn't know about that.

They'll know if you've been using any such aids already.  'Course, I suppose you could go blind at any moment.

Thanks guys. I found the Windows 10 ISO file at Microsoft. Downloaded it, installed it, and it activated just fine. Was gonna use Windows 8 for a bit, but it proved to be highly annoying. Had to turn off a bunch of privacy settings in 10, but otherwise I'm set. 

Windows 10, on clean install, is much faster than Windows 7 or 8. Now as far of the rest of it, that's another question, the UI and a lot of features of course suck.

I have a Dell I7 that had Windows 10 on it kona, with 4GB of DDR3 RAM, and it was really slow to me. So I just upgraded it to a Samsung EVO 1TB SSD, and now it's a LOT faster! Your system specs should be fine with Windows 10, but you also might consider putting an SSD in, to me it made a world of difference. 

Odd, a laptop that has to be thrown away if the hard drive fails?

Most laptops are that way. The only way to do anything is send it to the manufacturer, and it is limited. That is how you can carry it everywhere. It is called sodering.

Are there usb external ssd drives. That would work

Having installed Win10 on hundreds of systems I've found a HUGE bottleneck with hard drive activity on boot. 

Not entirely sure what it is that is happening but it drove me nuts on my home PC. (Dell XPS8500).

Boot time was unbearable with my SATA drive with nearly 4-5 mins before disk usage was below 100%.

I invested 90 bux on a Samsung 850 EVO 250GB SSD.

Now, from the time I see the BIOS log to a usable desktop... less than 10 seconds.

Note - This scenario is not confined to just my system. I've seen it on many others. 

Some laptops were 5400 RPM drives and I went to 7200 RPM and gained significant time as well.

Google Asus XM551. Now you have.

jafo did say the update this summer slowed one (more?) of his machines down. i'm assuming the w10 you grabbed would be the one with the update.. so maybe that's the reason?

Usually true.