The method is this;
1] Install XP first, make sure it is working.
2] Then, and only then, install Vista.
If you install Vista then install XP afterwards, the XP installation procedure will remove Vista's MBR, (Master Boot Record), and so Vista will no longer boot up.
If you install XP 'then' install Vista, the Vista installation will amend the MBR and not replace it, allowing you to dual-boot either XP or Vista.
The other problem is likely to be the deciding factor. This is, unless this laptop previously had XP installed, the laptop may not be compatible for XP. At the very least, you will have to hunt down the motherboard drivers, and all the other hardware and software drivers for XP before you begin the install. No easy matter, and full of potholes.
Mark
How can I insatal win XP while I preserve my vista home on my Laptop?

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