Installing XP on a Latitude E5510.

Your SATA (hard drive) controller is in AHCI mode, which requires you load a driver during installation by pressing F6.  The easiest fix is to put the SATA controller back to ATA mode, but you lose performance that way.  

To keep AHCI mode, you have to download the SATA drivers from Dell's support site or direct from Intel, put them on a floppy (use a USB floppy drive) and then press F6 at the very first screen of Windows XP installation so that it will look for custom storage drivers.  When you get to the point where you actually choose the driver, it looks like there are only 4 choices, but this is the bottom of a list of 20+ options.   Scroll up until you find "Intel 5 Series 4-port SATA AHCI".   The best way to figure out which one to pick is to look at Device manager in your Windows 7 installation before reverting to XP, but this will save you that step.  This will allow setup to finish properly.

** if you still get blue-screens...  I just about went insane trying to get XP installed on an E5510 that blue-screened no matter what I did, and finally I decided to check out the hardware.  Everything was fine, but the BIOS was on ver A03, which evidently causes bluescreens.   At the time I am writing this, the latest BIOS is A11, but you have to upgrade to A10 first.  At Dell's support site, after downloading A11, click on the description link instead of the download button and you will get a list of options.  Either on this screen or after choosing an option, you will see A11 again, but look for a link that says "alternate versions" or something like that and it will take you to the archived list for A10.