While I do own A5 Commercial. I have not installed or used it anymore since i've upgraded to A6 and A7 GameStudio. So I don't know for sure if it will work with XP, it will work with Windows 98SE. A5 can still be very good if you like to create a game for operating system older than Windows XP and Vista. A5 contain a software renderer which is pretty nice.

You could post a request on the forum that you like to purchase A5 from someone who doesn't use it anymore. The problem is that most ppl who have upgraded their version, can't sell the previous to anyone else. So, perhaps on Ebay etc..