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May be it is a silly question but i think its worth to me if it done.
I had worked on windows 7 ultimate but as you all know that there are still some software which doesn't work on windows 7 so I came back on windows XP. Now i want a dual boot pc and for that I have install the Windows XP first and now plan to install the windows 7.
My question is that is it possible to Boot from windows 7 if in any case I format the Windows XP. And I have a 500 GB external hard disk is it possible to install the windows 7 on it and boot Windows XP without this hard disk if sometime I want. For this I searched out this instruction but don't know how to follow them.
*Connect device to system and format it,now lets assume your external device has been assigned the letter D: and your cd rom drive the letter E:.Now open run ,in search box enter these: E:\I386\winnt32.exe /syspart:D: /tempdrive:D: /makelocalsource /noreboot .
Now press on Ok.
Now the installation wizard will appear on screen.This will take more time than installing widnows on a system.
After installation you can remove the hard disk and use on another computer. *

I mean if we set the system on dual boot it doesn't start until it doesn't find the second OS which is install through it. So i want to get rid of from this issue. Is it possible.

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3 Answers

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If you install Windows XP on an empty hard disc, it will create a combined boot+system volume. (This is a poor idea, and something that even the x86 PC world has finally moved away from in the years since Windows XP was released. Windows 7 when installed on an empty system will create separate boot and system volumes.)

If you install Windows 7 on top of that, it will update that combined volume in place, to replace the Windows XP ntldr with Microsoft's Boot Manager. The Windows XP boot+system volume doubles up as the Windows 7 system volume, with the Windows 7 boot volume a separate second volume (on that second hard disc). If you then format that Windows XP boot+system volume at a later date for some reason, you will indeed render your system unbootable, because it doubles as the Windows 7 system volume.

What you want is a separate system volume, so that both Windows XP and Windows 7 have separate boot and system volumes. They share the system volume — as they should since it is a system volume — and they each have their own boot volumes, that you can format and reformat at leisure, without each affecting the other.

Microsoft provides a lengthy procedure for doing exactly this.

Of course, you shouldn't need to touch the system volume. You'll always need your system volume. It is, as the name says, an essential part of the system. So don't go putting it on that removable hard disc that sometimes isn't going to be there at bootstrap time. But it will only contain, in a Windows XP/7 dual-boot setup, Microsoft's Boot Manager, the Windows Recovery Environment, and the Windows XP boot loader. You shouldn't need to touch it in normal operation, even for a complete reinstall of one of the operating systems.

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+1 for the link and suggestion to not keep on external HDD. Sounds very confident just try me it then I will tell you what happen. –  avirk Jul 7 '11 at 14:48
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Technically, a bootloader loads first before Windows. You just modify the bootloader to show entries for both Windows 7 and WIndows XP. The order to do this is first install XP, then install WIndows 7. Setup automatically detects you have XP loaded and creates an entry for XP on the bootloader automatically.

If it is on an external drive, you'll just have to tell bios to boot from the external drive instead of the internal HD. But why do that? If you use Windows 7 ultimate, then you have access to XP mode!! It allows you to run XP applications just like a regular Windows application, but it is actually running XP underneath.

For example, my my scanner software doesn't have 32 bit drivers, so I run it under XP mode. Looks just like another application, but it is running XP underneath.

enter image description here

edit in response to comment

Since you are installing WIndows 7 on a seperate partition, nothing XP does affects Windows 7 (well, there is [one hiccup]).2 And vice versa.

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I know about the Troubleshoot Compatibility and I have used it many time and it works but still on some software it doesn't work. I know about bootloader so my question is if sometime I have to format my windows Xp then how can I prevent to lost the data from Windows 7. –  avirk Jul 7 '11 at 5:03
    
Troubleshoot Compatibility != XP mode. A good article. arstechnica.com/microsoft/reviews/2010/01/windows-xp-mode.ars. I'll update my answer above for your comment. –  surfasb Jul 7 '11 at 5:07
    
Hmmmmm thanx for this nice article but i have been faced out a problem just few days ago with JDK 5.1 with derby it doesn't install on win 7. I tried everything but cudn't.:( –  avirk Jul 7 '11 at 5:12
    
XP mode is literally another machine. You can install the JDK under there while leaving your Windows 7 installation untouched. Try it. –  surfasb Jul 7 '11 at 5:13
    
I had run on virtual machine and its worked. But I don't like virtual OS........ –  avirk Jul 7 '11 at 5:17
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Windows 7 installation on an empty disk usually creates 2 partitions:

1 - System reserved ( about 100MB ) contains Windows 7 boot environment

2 - Windows 7 itself

In your case you can place the boot environment of Windows 7 (contents of System reserved) on the XP disk. If you install XP first on your internal disk then install Windows 7 on the external then Windows 7 boot environment will be placed on the internal disk and you will have a dual-boot created by Windows 7 installation process. In BIOS the order of disks should be internal (XP) first, external (Win 7) second.

If you disconnect the external disk you still can boot to XP over Windows 7 boot environment but if you try to boot to Windows 7 you will get an error.

You can make the boot choice for XP to be the default and rename the entry as Windows 7 installation creates the entry for XP as "Earlier version of Windows" for example with this tool Visual BCD Editor. Alternatively you can use Windows 7 "bcdedit.exe" command line utility.

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Thanks for this nice answer but in my question I shows some step to follow and the instructor says that its possible to boot on another PC with external HDD. –  avirk Jul 7 '11 at 6:17
    
The Windows boot environment can be created on XP disk AND on Win 7 disk. So if you change the boot order in BIOS - first Win7 disk second XP disk, the boot environment from Win 7 disk will be in control. If you take Win 7 external to another computer its questionable if it could boot there - Windows 7 is not a portable OS ! –  snayob Jul 7 '11 at 6:36
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