Then it is doubtful the issue is anything to do with XP since the operating system is not even beginning to boot.
You have a hardware problem of some kind and you have not provided any information about your system. We can make some assumptions. Since you mention keyboard LEDs flashing there is a distinct probability you are talking about a desktop system rather than a laptop. If that is so then troubleshooting a non-booting system has been described here many times before. Disconnect the power. Open the case. Re-seat all power and data cables. re-connect power and try booting. If no-go then disconnect power again and strip the system down to barebones. ie unplug power & data cables to all drives. Remove any PCI cards. remove all but 1 stick of ram. Leave only powersupply connected to motherboard. CPU with heatsink/fan. One stick of ram, keyboard & monitor connected to graphics. If you have onboard graphics port on the motherboard use that and remove any PCIe or AGP graphics card.
Connect power and try to boot up into BIOS. Any beeps? Any display? The way forward at each step depends on the results achieved.
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