This is a nice sentiment by Munich, but the many of the folks who are running XP and try and install Ubuntu 12 will be in for a nasty surprise -
32 bit machines without PAE will not load with most newer Linuxes. Most, including Ubuntu, no longer include 32 bit non-PAE kernels in their installers.
I found this out when I tried putting a modern albeit tiny Linux onto my FitPC 1 and an older EPIA motherboard - XP runs fine on these, but finding a linux is probably beyond the skill of most XP users. Jury rigging a different kernel in is definitely out.
A lot of older XP installs are also running on older hardware. Just giving away an OS will not magically fix this. And if these folks upgrade the hardware, it probably comes with a newer windows anyway.