The VirtualBox manual says the emulated graphics aren't
a hardware device as such (unlike the VPC2007 I use,
where an actual device driver installs for the graphics).
It's supposed to be some kind of built-in VESA driver,
that each guest OS would be using.For 2D displays, you can estimate video memory usage,
using a "frame buffer" as an estimate. If the graphics
are 32 bit, it takes four bytes per pixel of storage.
If the emulated screen was 1024x768 resolution,
then 1024*768*4 = 3MB or so. You can scale that a bit, to allow
for more than one frame buffer, off-screen memory or the like.
A fairly small number like 16MB should be enough to get started.The VirtualBox manual also mentions 3D. 3D can use "texture memory",
to hold textures for 3D. Another usage for 3D display memory,
is for "compositing" of application windows. WinXP doesn't do
compositing, and Vista Aero would be an example there.
MacOSX composites. Linux has Compiz (and some corny 3D effects).In a quick search, I see people suggesting 128MB as a video
memory number for VirtualBox, but that could well be overkill
for WinXP. I think MacOSX could composite in 128MB, and Vista
may have had that as a suggested minimum as well.*******As far as base memory goes, you'd have to go back and see what amount
of memory was recommended for WinXP at release. _xp "Memory Minimum = 64 MB RAM Recommended = 128 MB RAM or higher"The smallest quantity I've used, is 512MB (on a real WinXP machine),
which is sufficient to keep several application windows open, and
copy and paste between them. If you try and get too fancy, things
might be getting a bit tight, and paging out to the pagefile would
be undesirable.I run the majority of my virtual machines at 1GB, and that seems to work
pretty well. When I was running Windows 7, I think I set that to 2GB,
and that was OK. If I run Win98, purely for participation in File Sharing,
I run that with 256MB. But for your average virtual machine, I usually
choose 1GB. My computer has 4GB physical memory installed, and I've
run two regular VMs and one small VM at the same time.HTH,
Paul