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Your FIRST problem is.....
The hard drive is probably already full of one or more partitions made by Windows 7. (Most brand name computers have at least one smaller second partition on the original hard drive's brand name supplied software installation.)
You probably must free up space on the hard drive to install Windows XP on.
You must do this BEFORE you install XP...
E.g. Download the freeware Easesus Partition Master Home Edition.
Install it in Windows 7.
Use Easesus Partition Master to reduce (shrink) the size of the large partition Windows 7 is installed on to free up drive space (un-allocated space).
Then boot the computer from the XP CD..
Make a new partition for XP from the un-allocated space on the drive, then run XP's Setup.
"i want to get error during installation win xp2."
Do you mean you get an error while trying to install Windows XP Professional ?
You probably have a SATA hard drive.
If the XP CD is detecting NO hard drive, the easiest way of fixing that is to change a setting in the bios Setup.
Installing XP and SATA drive controllers, SATA drives; the SATA drive controller bios settings.
See response 2:
I stated in that....
"The detailed info about how you set the SATA controller mode or similar - it varies
depending on the bios version - is probably in the manual for your mboard model, in the descriptions of settings in the bios.
If you need help with that, you must provide us with the make and model of your mboard."
That's assuming you have a generic desktop system with a retail mboard model in it.
If you have a brand name system, similar applies, but we usually cannot find what you see in a brand name system bios version regarding that to refer you to on the web.
Whatever the setting is, when the files initially loaded from the XP CD cannot find SATA drives, it's presently set to SATA or AHCI in the bios, it's changeable, and at least one other choice is an IDE compatible mode of some sort.
You are supposed to install the older Windows operating system first, in order for the built in multiboot feature of Windows 7 to work properly. However, you can still install XP and use a procedure found on the web to make your system dual boot XP and Windows 7.
After you have installed XP, only XP will load.
Use a procedure found on the web to make your system dual boot XP and Windows 7.
OR - BETTER - use a third party multiboot program to set up dual booting XP and Windows 7. See Below.
There is a GLITCH that you may be concerned about.
When you have a system that is using the built in multiboot feature of Windows 7, EVERY TIME you load XP, it will DELETE ALL of the System Restore restore points in Windows 7 !
If your Windows 7 version has the bitlocker feature, Microsoft has instructions about how you can use bitlocker to get around that problem, however, not all versions of Windows 7 have that feature.
The same thing applies for multibooting XP and Vista.
The way that I got around that was to use a paid for third party multiboot program - BootIt! N.G. - to multiboot the system rather than the built in multiboot feature of Vista, and set the program so the Vista partition Windows itself was installed on is hidden from XP when you boot XP - there is a tutorial video on their web site about how to do that, for Vista or Windows 7.
NOTE that not all third party multi-boot programs are compatible with Vista's and Windows 7's support for the ACPI features of the mboard's main chipset. BootIt! N.G. IS.
If the program is not compatible with that, your computer WILL NOT "wake up" (after the main chipset drivers for the mboard have been installed; they should always have been installed) after it has gone into an ACPI mode - e.g. Standby, Hibernate modes.
You may be required to make a small partition on the hard drive for the third party multi-boot program (I did that for BootIt! N.G.).
E.g. you can do that with Easeus Partition Master Home Edition, after freeing up drive space (un-allocated space) on the hard drive for it.