how old is the laptop?
the hard drive is still being detected sa bios right? baka may bad sector lang na natama sa OS area
do you have the XP installer disk? use that if you have it, then do a repair installaion (mas maganda kung nasa sayo rin ang driver disk ng laptop in case need palitan)
pag sa bios hindi na madetect ang hard drive then need tanggalin yun and salpak sa enclosure or other computer to test and hopefully rectify any errors
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btw, just to correct some things mentioned in this thread
yung IDE, and AHCI, will not matter. you can use SATA IDE on windows 7 (you can also use AHCI on XP, tricky lang pag nag switch ka if already in one mode-madaming gagawin), its not true that you cannot install if its on SATA IDE mode, its just that AHCI is the better choice for so you can take advantage of the benefits (i.e. hot plugging, raid mode). its basically IDE is old tech, AHCI is new tech