It's very likely that you're having a SATA driver issue. Virtually all modern laptops today have SATA hard drives, and Windows XP doesn't come with SATA drivers.
If this is the issue, there are two possible solutions:
The first solution is to disable SATA Native Mode (or a similar option) in your BIOS if available, allowing your hard drive to be detected, and for you to be able to install Windows XP. However, the disadvantage is the performance degradation, since SATA native mode is disabled.
The second solution is to obtain the correct SATA driver for your hard drive, and install it during the Windows XP setup procedure by pressing F6 when prompted. Instructions here: HEXUS.net - Guide :: Installing Windows XP with a 3rd party SATA/RAID driver : Page - 1/1
It's also possible to install a SATA driver when booted into Windows XP after performing the first solution (which is what I did), however it can be difficult, since driver installers and Windows XP device manager doesn't know a SATA hard drive is present, since SATA native mode is disabled. A guide outlining this procedure, but for Intel SATA controllers only, is available here: My Tech Blog: Enabling SATA Native Mode after XP Install