One of my machines keeps producing errors starting the virtual machine. https://uspex-at-home.ru/prediction/show_host_detail.php?hostid=141.
It is running with virtualbox 6.1.34 on Win 7 and running the 4GB tasks. CPU has hardware virtualization support and it is enabled.
I have another computer which is running with virtualbox 6.1.34 on Win 10 and running the 6GB tasks and is working fine..

I am unsure if the windows version makes a difference, if not then I cant find what would be causing the error.
In the Stderr output I find "More details may be available in 'C:\ProgramData\BOINC\slots\2\USPEX_VMVASP_52769183\Logs\VBoxHardening.log'" this however doesn't help much as the slot is over written by new tasks.

I have tried recently with a new machine, same OS and VBox versions (boinc 7.24.1, Windows 10, vbox 7.0.6) as the machine that works without a problem yet I am still having problems getting the task beyond the startup phase. Any help getting the machine to run would be appreciated.

Are there some sort of additional stuff I need like a different version of VC++ from Microsoft?

The problem is not in the C++ version.
Please check the installation path to VirtualBox.
And also set the VBOX_MSI_INSTALL_PATH variable.