Eww c'mon just because MS stopped the XP support doesn't mean that the OS cannot be used anymore.
As long as you have FW and AV software that still works with XP and recives updates, it shouldn't be nearly as risky as your minefield methapher.
In fact if there are less ppl using this OS it becomes unattractive for hackers as a target plattform while newer Versions like Win7/8 are becomming more attractive.
Honnestly i don't see a reason why someone who's using an old computer with XP should update the OS unless a seriouse hardware update is made too.
On my PC I've been using Win7 for a while now, but only since i updated my hardware and even before that i used dual boot with XP Pro 32bit and Win7 Pro 64bit.
My laptop on the other hand recived a downgrade from Win8 OEM to Win7 Pro 64bit.
Still using the Win8 RTM theme for it, since i prefer the simplicity of the design.
Maybe, if Win9 will be less focused on Mobile touch devices and combine the best things of 7&8, i might considder an upgrade.