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From:	"Alexei A. Frounze" <alexfru AT chat DOT ru>
Newsgroups:	comp.os.msdos.djgpp
References:	<cbc DOT 10c299c6 DOT 33643fde AT aol DOT com>
Subject:	Re: no DPMI memory under Windows vista
Date:	Sat, 28 Apr 2007 03:39:31 -0700
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Reply-To:	djgpp AT delorie DOT com

Simply put, a virtual machine is effectively a fake computer, an emulated 
computer, a computer in computer. It allows you to install another OS within 
the virtual machine on top of the OS that you already have and work in that 
VM as if that was a real separate computer. The vurtual machine utilizes the 
real disk and RAM and some of the CPU time to function. The virtual machine 
is comprized of virtual devices, that is, it has a virtual disks (inside a 
file on the real one or can use floppy/CD/DVD directly), virtual display (a 
window), virtual network and so on. The virtual machines allow you to try 
various OSes and software w/o damaging your OS, it sandboxes that software. 
They also allow to change various system parameters inside them (disk/RAM 
sizes, etc). You may have many different VMs at the same time. More on this 
(if this is an entirely new topic for you) can be found here: 
<http://en.wikipedia.org/wiki/Virtual_machine>. It is very easy to install 
Virtual PC. It may, however, take some time to create a working VM inside 
it -- you need to create it, specify disk/RAM sizes and other parameters, 
then you need to boot the VM from a floppy/CD image file or from the real 
floppy/CD to install the OS inside the VM just like you'd do on the real PC. 
Then you may need to set up either networking or share folder to be able to 
transfer data between this virtual OS/machine/PC and your normal OS. I don't 
know if any network in DOS works, but if you install in there windows 9x/xp, 
transferring data will be simple.
Cautions: a running VM may take up significant amount of RAM, disk size and 
CPU time. It generally runs slower than it would have had it run on the real 
hardware directly w/o any virtualization/emulation.
Sound may not work. I haven't used VPC much (just a few times) and in older 
versions there was no sound support. I don't remember if it's in 2007 
version or not.
VGA planar modes may be noticably slower compared to 8/16/24/32 bpp graphics 
modes.

If I had to make a DOS VM from one or few DOS installation/bootable 
floppies, it would take me about 30 mins to create a VM and install DOS in 
there. YMMV, obviously. Windows installation will take more time, 
apparently, just because it's much bigger. But, once it's installed, you may 
save the VM file(s) as the base and if/when you screw the VM, you can pull 
those files with the freshly installed OS and start over in no time.

VMs are your friend.

HTH,
Alex

<Sterten AT aol DOT com> wrote in message news:cbc DOT 10c299c6 DOT 33643fde AT aol DOT com...
what's VM,VPC,... ?

it can't be so difficult, no need to modify the kernel, I assume.

How much time do I need to inform,install,learn about a way around it ?
(just an informal estimate) 

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