Installing 21.04

[Ralf Mardorf]

I'm running a Windows 7 as VirtualBox guest with 512 MB base memory and
39 MB video memory and a Windows 10 VirtualBox guest with 2048 MB base
memory and 128 MB video memory on a Linux host with 8 GiB RAM.

The "used" memory with just a PC turned on and no foreground apps open
at all, is not necessarily equal to the really needed memory. Probably
Windows 10 does what Linux always did and still does. It does use all
available RAM and does free RAM, if needed. That memory is used at some
point in time, does not mean that it is needed at that moment.