fix unallocated space mistake  

My daughter asked me to do a fresh install of win 10 on her win7 Samsung laptop but I installed it in the unallocated space without pressing the new button which I now know sets primary and system partitions.
I then transferred all her data, music, photo, and videos from external HD back on to the laptop with win 10 now installed.
Can anyone tell me how to fix this or do I need to start from scratch, or would it cause any problems to just leave it as it is.

It depends.

How large is the partition you installed to?

If you still have the data on the external drive, I'd do another fresh install, but that's just my OCD.

The hard drive is 1 Terabyte so 931 GB unallocated space.

wolfdog said:

The hard drive is 1 Terabyte so 931 GB unallocated space.

My experience? Redo it. Or maybe check Computer Management, Disk Management to see if you can Extend the C: partition into that unallocated space. It usually works as none of the OS files have to be moved.

[On the other hand, shrinking an OS partition to allow for creating another partition can be problematic as some of the OS files can't be moved which can limit how much shrinking can be done.]

As for the OS files themselves, there's usually 1 or maybe more that get 'fixed' during the OS install as to location in the partition that can't be moved.

It is activated with the win 7 serial No. that came with the Samsung laptop. I cant check if there is a recovery partition or EFI as my daughter has taken her laptop home. I don't understand about Partitions EFI, etc. I just saw a video on this site that said press New and the unallocated space became Primary partition and System partition but I viewed this video after I had done the fresh install in the unallocated space on my daughters laptop so whatever I have to do to fix it will have to wait till I next see her.
But I have the same laptop as her and I am going to do the fresh install on mine so can you tell me exactly how to deal with this stage
bearing in mind my knowledge is low.

wolfdog said:

My daughter asked me to do a fresh install of win 10 on her win7 Samsung laptop but I installed it in the unallocated space without pressing the new button which I now know sets primary and system partitions.

I'm not sure what the issue is. Installing to the unallocated space is the best way to do a clean install of Windows 10. Let Windows setup create the partitions it wants. Then if you want a separate data partition just use MiniTool Partition Wizard free to shrink the OS partition and create a data partition.

If you post a screenshot of disk management, we can see what is going on.
Disk Management - How to Post a Screenshot of - Windows 10 Forums

I cant post a screen shot I don't have the laptop here ,are you saying that I have done right by installing it in the unallocated space and that windows may have created the primary and system partitions it needs anyway.

wolfdog said:

I cant post a screen shot I don't have the laptop here ,are you saying that I have done right by installing it in the unallocated space and that windows may have created the primary and system partitions it needs anyway.

Absolutely yes. I've done probably 10 clean installs of Windows 10, each time when I want a brand new install, I select the custom install option, delete every partition on the hard drive, select the unallocated space and install to it. You get 3 or 4 partitions depending on if it is UEFI or legacy bios - a system reserved or EFI system partition containing the boot files, an OS partition, and a Windows Recovery Environment (RE) partition. UEFI will also get a small Microsoft System Reserved (MSR) partition.