First off, Do you have all the drivers you need after XP is installed. What brand is your laptop, you should go to the
manufacturers website and look up the compatible drivers. I have seen a majority of Dell Laptop’s that have been able to downgrade to XP. Second, You might need a SATA driver for your machine because it is not recognizing the HDD. So go find out the brand of your machine and look up the drivers and see if that works out. Also you might want to check if your machine is 64-bit or 32-bit.