Making 2 computers into one new computer

[CoZzaBoZza]

This is probably one of the most confusing things you'll ever hear, but anyway.

 

a while ago, I had two computers. One was my mums, an old HP z240 workstation with some slight upgrades, and mine...a very old throwaway desktop that didn't work very well. Long story short, mine got exterminated accidentally by my brother, and the only salvageable part was my Hard drive - a WD5000AAKX - which was fine, it contained all my files anyway, so no issues. later, I plugged that hard drive into my mum's computer and this was also no problem. 

The issues begin about 6 months later. Mum started to run out of storage, she has a Samsung SSD with about 2gb of storage left in it. Over the course of a few weeks, I built up this computer until the only original parts were the RAM and the GPU, everything else got replaced. In the process I brought a new SSD - Samsung 990 pro, without a heatsink, 1tb - thinking that I could just put the stuff from my HDD and mum's SSD onto this and call it a day. 

This is of course not the case, because although the Samsung wizard could bring my stuff over, it cannot do the same to mum's SSD, because data migration isn't supported, so I tried to do it myself by just Ctrl+C, Ctrl+V'ing everything. This didn't work, because it 1 - kept freezing at 7% on a file called AppvlsvSubsystems32 and 2 - I obviously can't just combine the different Program files, Users, AppData and Program Filesx86 folders...

 

Now i'm stuck, because all of my hard drive is on the new SSD, none of Mum's can get on there without having issues and the main problem is still present - I want this to be 1 computer, with 2 users instead of 2 different computers that can only be used correctly by entering bios and changing the boot drive. This used to be easy on the old motherboard, which was a HP, but now I cannot figure out how to do it on the MSI B550-a pro board. 

 

any tips would be appreciated.

 

TL;DR - I need to get 2 different windows users to go from separate disks to the same disk, without losing files.

[Sjaakie]

for the new install you'll need to install all programs again. Not just copy programs files etc. indeed. Personal files / documents can just be copied.

[jaslion]

Backup your files ans reinstall all programs after a fresh install. No other way to do it

[CoZzaBoZza]

Alright thanks. Have started to do that for my files, will have to bring over mums personal stuff and installers

 

After that if I install her stuff on the SSD, can I just delete all the old stuff? Or is there anything like temp files, cache or AppData stuff that I need to do something else with?