I realize the title is complex and I apologize for that. However, this is what I have and I'm stuck.
Background
My desktop computer (Intel i7, 12GB ram) is running Windows 7 64-bit. I would like to change it to Ubuntu but I have some programs which only run under Windows. So, my plan was to run Win10 in VMware (which I have used for years and quite like) under my new Ubuntu for those few apps which require Windows.
Testing
Since this is my main computer, I do not want to take any risks with it until I have everything fully tested. This means, I need to make sure I can run Win10 inside VMware inside Ubuntu. Well, good thing I tested because I was unable to get VMware running on Ubuntu. While it might be possible, I am not looking for a software solution which only experts can implement (and I am certainly NOT an expert on Ubuntu, I am a newbie at best).
Alternatives
After some searching, I found decided to use VirtualBox inside Ubuntu (which is still inside VMware). I exported my VMware Win10 to the more universal OVF format, copied it to Ubuntu (which introduced a couple more days of time chewed up as I had to deal with adding drives to Ubuntu, etc.). I never got that to work, so I did a fresh install of Ubuntu 64-bit inside VMware with a 200GB hard drive to avoid the earlier problems repeating.
Current situation
Now, I have Win7 with VMware 12. Inside a VMware instance is Ubuntu 64-bit (16.04 LTS). Inside Ubuntu is VirtualBox 5.1.18. I am trying to run a VMware instance of Win10 which I created under Win7.
The problem is when I read https://forums.virtualbox.org/viewtopic.php?f=6&t=49636 it encourages me not to use the OVF but rather use the VMware .vmdk files while creating what seems to be a VirtualBox shell around those .vmdk files.
The problem is, I can only see 32-bit options in my VirtualBox (everything else is 64-bit). I have read other posts both here and elsewhere which talk around this issue but nothing which seems to address my situation, which seems unique until you think about other people wanting to move from Windows to Ubuntu and wanting to test things first.
It's long, I know. However, I would be quite happy for anyone's comments pointing me in the right direction.
It might be important: I really do want to use the existing Win10 VMware instance I have because I have spent a lot of time getting it setup properly and do not want to go through all that again.