mostly Virtual machine. One time, a Longhorn Build "damage" my HD testing physically... I recovered with Hirens Boot

Depends on whether it‘s a broken pice of Alpha or a quite usable Beta
For the KDE Alphas from Trunk I use my virtualbox, when it becomes available in Kubuntu repositories, I install it to my notebook and as soon as RC1 it‘ll go on my production machine as well. Never got any problems with that.

Since I cannot use my primary, laptop, and old physical computer to test betas, I can use Virtual PC/VMWare for testing Windows betas as well the Macintosh emulators for the Mac OS Classic betas.

VM. I've tried to use Longhorn 4074, but unfortunately I couldn't find working drivers for my videocard...

i always using winxp virtualbox

You can try the Hounsell drivers.
Here is the link to download them.
http://www.microsoftcollectionbook.com/ ... ldriverkit
They're hosted on the MCB site, which is useful IMO so you should take a look at that as well.

Using Virtual Machines, I don't have any empty pcs yet lol

If the beta is old i use virtual computer (Windows Longhorn, Whistler, ...).
If the beta is new i use physical computer (Windows Vista RC1 (Nov2006), Windows 7 Beta (Oct2009), Windows.next Beta (Sept2011), ...)

Virtual, putting pre-release OSes on physical machines would be pretty dumb, to be honest.

I do it if I've got hardware from that era. Best way to see what the testers had to put up with is to use physical machines.

Yeah, but for example multi-booting it with your main OS on your main machine would be potentially suicidal. I wouldn't install it on a working older machine either.

I would install just ONE Beta Windows for testing it out. Without having an exist Windows.

As not all Beta Windows' versions may support hardwares and memories. And may damage your current installed Windows.

For sure, a virtual machine.

I use virtual machine cause if something goes wrong on the virtual machine it is not as bad when something goes wrong with your physical computer. I only install RTM versions of operating systems on my physical computer.

I would install an RC build on my main machine, maybe a beta on my laptop if its quite stable.

The Windows 8 builds that have been leaking recently I would only install in a VM.

now, with Windows 8, I'm using phisycal partitions to install them

My eMac can't run much.
I wouldn't even try to run VMware Fusion on it.

I would recommended using virtual for betas.
Edit:
Edit2: Typed the number wrong on the offtopic post. Changing it.

I use both, virtual and real computer.

I mostly use a physical computers, because I want a realistic view on how an OS runs. When that doesen't work, I switch to virtual.

I mostly use virtual machines, but when I have hardware of the epoch, I try them.

Virtual, wish my old P2 was working

I use physical computer for testing systems at-full-speed and to get a real experience. Therefore I'm using Virtual Machines to make my life easier (really, my second computer hasn't got a monitor, so I need to un-plug it from main and plug it to testing area, it's annoying, but It will change in future )

Virtual is more safe to test the Beta's

Certainly a VM. I have a 1996 Thinkpad that as soon as I get that floppy drive in, I might try to install Connectix Virtual PC 1.0 or maybe 2 and then put Windows 3.1 build 34e on it.