Drained with Windows 10

Jheeez, what a mess around this has been with the install of Windows 10, having a right nightmare with a laptop for a friend of mine, where do I start?

Dell Inspiron N5030 - Windows 7 Home Premium X64 - OEM KEY

Windows 7 all updated and the upgrade prompt active, all good to go :) installed, upgraded and activated. left this about a week with my friend.

Computer does seem to be slow at points and looking at the hardware, 3GB RAM and a Dual Core CPU then X64 might be a little too much, However, I go and run the reset feature after extracting the converted key from Windows 10 for peace of mind.

Reset feature is running and running, I fall asleep and after waking up I get: INACCESSIBLE_BOOT_DEVICE.

Oh Dam, I got Windows 10 Pre Boot Environment on my USB, run DISKPART and see the partitions available, I did try and run a reset again and last know good configuration, no joy!

I go ahead and perform a clean install but for X86 version instead because of the laptop's hardware, it was activated and should have passed all the information to Microsoft too.

Please enter product key, easy enough I got this in the bag - INVALID

I skip this and hope the internet updates might help me, no it has not - I just don't understand? I have done everything from the book and it's screwing my brain. (Error code: 0xC004C003)

The only thing I can think of is that I'm trying the converted key on a 32bit system when it was 64bit? or because I upgraded with a OEM Windows 7 key?

Anyone with the same issue or experience? I'm just sitting here thinking about taking it back to 7 and leave it for a while.

I would go back to Seven, take a break and then start it again.

The only thing I can think of is that I'm trying the converted key on a 32bit system when it was 64bit?

That usually doesn't matter.

or because I upgraded with a OEM Windows 7 key?

I also would go back to Win7 w/SP1 then do all the updates which will include the files to let you reserve Win10 Upgrade then install it when prompted. Later you can do the clean install if necessary. I've not had to enter a Product Key on the 7 Upgrades I've done.

Yes, I'm going back to 7 on this one.

Might make it a 32bit system as it will be less strain on the hardware.

Thanks :)