Success! I made it work! I'm playing Six Ages in a Win 10 virtual machine running in my Win 7 physical machine. Turns out virtualbox has some issues with nvidia cards and 3d acceleration. I'm sure other people are interested, so here's a step-by-step:>What you need to do to run Six Ages in a Windows 7 machine
Step 1: Download VMware Workstation Player 15.5.6 from https://my.vmware.com/web/vmware/downloads/info/slug/desktop_end_user_computing/vmware_workstation_player/15_0
It requires an account, but it's free for non-commercial use.
Step 2: Download a Windows 10 iso from https://www.microsoft.com/el-gr/software-download/windows10
You don't need a key for what we're about to do.
Step 3: Install and run VMware. It will ask you for your Win 10 iso and create a virtual machine.
Step 4: Run the Virtual Machine. You will go through the Win 10 installation process. I recommend Win 10 Home, but you can pick whatever for most options. I also recommend performing this step offline (turn off your wifi or disconnect your ethernet cable) so you can skip creating a Microsoft account.
Step 5: Inside the virtual Windows, download Six Ages from your site of choices and run Windows Update. You'll need to reboot the virtual machine after installing the updates.
Step 6: After rebooting, go Player -> Manage -> Install VMware tools. This'll mount a virtual cd with some setup files. Run the appropriate setup for the OS you installed (probably x64). After it's installed, you'll need to reboot the virtual machine again. This step is required to enable 3d acceleration, and is the last thing you need.
Step 7: Run Six Ages. Enjoy the game on your Windows 7 PC!