It depends on the system features your Windows XP have. Here are the minimum system requirements that are posted by Mojang:
The recommend system requirements to run minecraft more smoother and more playable are:
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Almost all games being released still support Windows XP.
No. It won't work on XP SP2 or anything higher. It will work with XP SP1 however.
Yes, Minecraft works perfectly. Minecraft is programmed and runs on java, so that it can be played on a variety of platforms - including Mac, Windows, and Linux. If Minecraft doesn't work for you, you may have to update your version of Java.
Yes, it runs if you set it to XP compadibility mode.
Yes, it should work fine under Win7.