>most MB manufacturers didn't enable it.
So it would be a bad idea to count on it I think.
There's a lot more reasons I'd discount this solution. For one - the problem says a 32 bit machine. It doesn't say a 32 bit Intel machine. It doesn't say a 36 bit machine - which is essentially what PAE gives you if its enabled. It says - a vanilla 32 bit machine.
I'm not saying PAE is bad. I'm not saying it isn't widely available. I'm saying it is outside of the problem definition.