This is an often problem.Many people that have Windows Vista or Windows 7 are having problems installing Windows XP back.The reasons for that are few:
-First reason can be what johnb35 already mentioned.I had the same problem
installing Windows XP on my new laptop and all I did is that in the BIOS I changed the AHCI to COMPATIBILITY.So try this first and if it doesn't work,try the rest of the things below...
-Second reason...BOOT SECTOR.This is usually the main,the hardest and the most unknown task to the most people.Every Windows operating system creates its informations in the boot sector in order to be able to boot after the BIOS has been loaded.But why is this hard for many people?Well...the reason is simple.PEOPLE DO NOT UNDERSTAND THAT FORMATTING THE HARD DISK DRIVE AND MAKING THE FRESH WINDOWS OS INSTALLATION DOES NOT DELETE THE PREVIOUS INFORMATIONS FROM THE BOOT SECTOR OF THE PREVIOUS WINDOWS OPERATING SYSTEM.For example lets say that you want to install Windows 2000 over the Windows ME.You will simply put the Windows 2000 CD in the CD/DVD-ROM disk,boot from it,delete all the existing partitions and make the fresh install of the "newer" operating system...And yes.This will work and you won't have any problems.You are probably asking yourself why.Well the reason is also simple.Back then Microsoft DID NOT programmed their Windows OS to hold old informations in the BOOT SECTOR from the previous OS such as Windows 98,ME and so on...and therefore you had NO PROBLEMS installing other Widnows operating systems such as Windows 2000 and XP...The Windows Vista and Windows 7 are NEW technology from Microsoft.Those 2 new operating systems are working different then any previous OS they made.The bad thing is that Microsoft programmed Windows Vista and Windows 7 to store their informations in the boot sector which CANNOT be deleted with the previous Windows operating systems such as Windows 2000 and Windows XP what wasn't the case before Windows Vista came out.Since Windows Vista came out,people are having problems returning back to earlier Windows OS after they have installed Windows Vista or even Windows 7 on their HDD.In short...Windows XP or ANY OTHER PREVIOUS WINDOWS VERSIONS CANNOT DELETE THE INFORMATIONS FROM THE BOOT SECTOR IF THE WIDNOWS VISTA OR WINDOWS 7 WAS ALREADY INSTALLED ON THAT HARD DISK DRIVE.So Windows XP or ANY OTHER previous Windows versions CANNOT delete the informations from the BOOT SECTOR that Windows Vista or Windows 7 created.Now you probably ask yourself why.Well the answer to this question is very simple.Because Microsoft decided to do it that way.And why did Microsoft decided to do that?Well simply because on that way they are forcing people to use the newest Windows operating systems so that they can earn a LOT of money.Anyway there ARE ways to COMPLETELY format the entire HDD and the entire BOOT SECTOR so that you can again install older Windows versions such as Windows XP with no problems at all.One of the ways is to use the simple DOS program called KILL DISK 4.1 directly from your USB stick.That DOS tool will completely format your entire HDD including the entire BOOT SECTOR.And after that you can install ANY Windows version on your computer with no problems at all.
Except you probably won't be able to install Windows 95 and Windows 98 FE because your propcessor probably has a lot more then 300 mhz.
-The third reason can also be what wildbill already mentioned.Yes it can be the HARDWARE INCOMPATIBILITY.Maybe Windows XP just isn't compatible with your hardware at all.This is VERY rarely,but if thats the case,then forget about the Windows XP.
-The fourth reason can be that your CD-ROM disk of your x86 or x64 bit edition of the Windows XP is damaged.If thats the case,you CANNOT install Windows XP or ANY other Windows OS if its CD or DVD-ROM disk is damaged.
-The fiveth reason.Be sure that your CD/DVD-ROM drive,hard disk drive and other hardware components in your computer are working properly otherwise you can't install any OS on it...
-Sixth reason.As for the RAM,you can have even 50 GB of RAM,but thats NOT the reason why you can't install Windows XP back!If you have more then 4 GB of RAM,Windows XP x32 will detect 4 GB of RAM,ignore the rest and thats it.So no.Too much RAM is NOT the reason for being unable to install Windows XP.You did say that you also tryed XP x64 bit edition and that it didn't work so here I can tell you for SURE that too much RAM isn't the reason because x64 operating systems can detect up to 128 GB of RAM and I am sure you don't have so much RAM in your computer.
So here you are.In very short I wrote you why you might be unable to install Windows XP.Try to do what I told you here and tell us if you were able to install Windows XP on your computer.
By the way if you don't know how to prepare the KILL DISK 4.1 to run directly from your USB stick inside of the DOS environment,tell me and I will connect to your computer with the Team Viewer 4 and do the job for you and explain you how to use it.
Cheers people and MERRY CHRISTMAS TO EVERYBODY!!!
