Never change any settings

Which are what?
Where from, BOINC Manager or the web site?
When in doubt, post the contents of your global_prefs.xml file and if it exists the global_prefs_override.xml file. These files can be found in the BOINC data directory, by default at C:\Programdata\BOINC\
This is a hidden directory, so either fill in the path directly in Windows Explorer and go there, or set Windows Explorer to show hidden files and folders.

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Things I notice, from the global_prefs_override file - so the local preferences:

<vm_max_used_pct>100.000000</vm_max_used_pct>
<ram_max_used_busy_pct>75.000000</ram_max_used_busy_pct>

You are telling BOINC to use 12GB of RAM and when that's full to use the whole of the Windows page file. If you didn't change the Windows page file setup, that will be double the size of your memory, if not more. And since you tell BOINC it's fine to use all that space, that's what BOINC does as soon as it runs out of memory.

So the thing here is to change those settings.
<code>vm_max_used_pct 100</code> -> <code>vm_max_used_pct 25</code> and <code>ram_max_used_busy_pct 75</code> -> <code>ram_max_used_busy_pct 25</code> are big enough values.

Edit: in layman's terms that's:
BOINC Manager->(View->Advanced view->)Options->Computing preferences->Disk and memory->When computer is in use, use at most 25% and Page/swap file: use at most: 25% -> OK.

With the latter you tell BOINC to use 4GB of RAM and the first a maximum of 25% of the page file. If you then set the Windows page file to a strict number, see for that advice this page, it should behave more normally.

If at the end of all this it still overflows so dramatically, please post back about it.
We'll check with some debug flags then what it says.

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Reading this thread over at LHC, they should be aware of the problem of the LHCb application needing 2GB per task, but reporting just 480MB being used to BOINC. This is why BOINC allows more tasks to run than there is actual memory in the system. It can't accurately act on this when the application isn't telling it what is being used.

That thread also advises to set up an app_config.xml file to force BOINC to just run that many tasks so that memory use stays under your maximum.
All I can further do is report this to the BOINC developers and hope they talk about it with the project that their applications should return the correct memory usage.

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Question from project administrators, which version of VirtualBox are you using? If the version you state in your signature, do know that that one doesn't work well with Windows 10.
Update to 5.1.14 in the least.

David has in the mean time put a probable fix in for memory problems, but that won't show until we get a next client - whenever that is.

Also, can you run one of the projects to capacity and then enable mem_usage_debug via BOINC Manager->Options->Event Log options->check mem_usage_debug->OK.
Next open the Event Log, CTRL+SHIFT+E and copy/paste the messages from there.

I know this copying of the log could be problematic when your system is neigh on crashing, but do know that it's still logging all this to a file on disk as well, so if you need to reboot, that's no problem.

After a reboot, pause everything, then navigate to your BOINC data directory, default a hidden directory at C:\Programdata\BOINC\ (so just fill in the path in Windows Explorer and hit Enter) and find stdoutdae.txt, open it with Notepad, scroll to the very end and select the last 40-50 lines, post those here.

Don't forget to disable the debug flag, BOINC Manager->Options->Event Log options->uncheck mem_usage_debug->OK.

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