I want to download this old game I found, Roller Coaster Tycoon 3 Platinum. I am on windows 8 currently and it can only be run on windows "98/ME/2000/XP". I am curious what would be the best to download, and how dangerous/permanent/possible it would be.
To clarify what virtual machine is, according to Wikipedia:
A virtual machine (VM) is a software based, fictive computer. Virtual machines may be based on specifications of a hypothetical computer or emulate the computer architecture and functions of a real world computer.
You can simply download one of the virtual machine software, install your XP in one of them and play the game there instead of downgrading from 8 to XP! You have to refer to their website for installation instructions. VirtualBox is a good place to start.
XP is on the end of its suprisingly long shuffle towards obsolesce. The world has moved on, and we have shiny things like composited desktops, and less obvious and more awesome things like better security protocols.
Hardware has moved on - you'll have trouble finding drivers, and as time goes on, less and less software will support your system. You'll be stuck with older versions without the benefit of new features.
Your system might even be one that uses UEFI, and XP may not know what to do with it without tricking it into thinking its a classic bios (never tried it myself).
Soon it would have rode of into the sunset, or more accurately, needs to be taken out the back, shot. We need to bury XP, not praise it.
In short, its a terrible idea - especially to run a game.
On the other hand, this game exists on steam, and looking at the specs, there's no plausible reason it wouldn't run on a modern OS. For really old games, picking it off steam or GOG is a good idea if you want to play a game, but can't be bothered to keep track of the media or beating it into running.
You can attempt to run the game in compatibility mode.
Downgrading to XP from 8 would be taking a huge step backwards in functionality. Not to mention, if you are using a newer PC, or a PC with 64-bit drivers, you may not be able to find equivalents for 32-bit XP.
Why not run XP in a virtual machine, then run the game on there? You can find plenty of information about that around.
In Windows 8 or 8.1 you have the Virtual Machine Hyper-V just enable it and install Windows XP in it. Or try to run the game in the compatibility mode. You can even install Windows XP to dual boot with Windows 8, but do not downgrade Windows 8 to XP just for a game.
Windows 8 is a modern OS, it is more secure, has better performance, is more reliable and in general is in every aspect better than Windows XP. A downgrade would be a huge step backwards.