Hi all, I'm new here.  I've been told several times that what I'm trying to accomplish can't be done but I don't understand why. 

Basically, I have 2 laptops.  My main one is going into the shop asap.  It needs a new fan and HP has indicated that they will conveniently wipe my hard drive for me (isnt that nice of them?).  So I need to get a backup working copy going.  I have a "loaner" laptop (which is an IBM) but its HD is only 30gigs.  Mine is 80gigs and I can barely fit any of my programs on there let alone files.  That's fine though, because I have an external usb 250gig harddrive.  I'd like to essentially copy my laptop to the external harddrive, then boot the loaner laptop using that harddrive instead of its built in one.  Why can't this be done?  If it can, is there anyone out there that can help?  I will be computerless
for about a week, and would like to be able to conveniently copy my stuff (files, programs, users, application data, etc.) BACK to the freshly wiped HD on my laptop when it comes back.  Both machines are running XP (mine is the Media version, the loaner is Pro).  I also have a version of XXCOPY and Norton Ghost 10 but haven't yet figured out how to accomplish this.  I do have the loaner laptop setup to dual-boot, offering either the loaner's hd or the usb hard drive, however it won't start due to a "windows config" error of somekind, so perhaps I'm not doing it properly.

Any help is greatly appreciated!

EP, thanks for the reply.  I can get it to BOOT from the external, however, windows won't load from that point.

To diagnose lilqhgal's problem, there are three completely different issues that must be addressed:

• Is the hardware similar enough to that on which Windows was initially installed?
• Does the hardware in question support booting from a USB hard drive, operating system notwithstanding?
• Is Windows capable of booting from a USB device?

Let's take the first issue.  Rad hinted at this.  During installation, Windows is customized to the particular hardware devices that comprise the system on which it is installed.  These devices include things like the bios, motherboard chipset, audio chip, graphics chip, disk controller, etc.  Every time you boot the computer, Windows loads the appropriate drivers for these predefined devices, so it works fine if these are still the right devices.

If you move the hard drive to a different computer, it may or may not work.  Windows has limited ability to notice when devices have changed, and reconfigure itself by installing the correct drivers for the new devices.  If the hardware in the new system is similar enough to the original system, you can usually get away with it.  But if the hardware is too different, Windows can't even get enough of itself booted to start figuring out what's different.

At the very least, lilqhgal will probably have an issue with the oem Windows version.  Most oem versions are locked to the computer's bios.  Move the hard drive from a HP computer to another HP, and it may be okay because XP still sees a HP bios.  But you may well have a problem trying to boot a HP version of XP on a computer that does not have a HP bios.


Now for issue two: does the computer hardware support booting from a USB device?  Legacy bios chips couldn't even "see" the USB port.  Sure, you might be able to load a USB driver after booting to DOS, but that's a moot point when the question is booting from that device.  Later, bios chips began including drivers to natively see USB devices.  Most recently, bios chips began adding support to actually use a device on the USB port as a boot device.

However, this whole area is not very standardized, so caveat emptor.  In some systems, you can boot from USB flash drives, but not USB hard drives.  Some systems poll only one or two USB ports for boot devices, so you may have to connect the drive to a specific port.  You're completely at the mercy of the bios designer here.  If the bios can't see the USB device or doesn't support booting from it, nothing else matters, the whole show stops right here.


Now for the third part.  For background, consider this relevant portion of a typical boot sequence:

• load 16-bit "real-mode" device drivers for the hard drive, video display, etc.;
• locate the hard drive;
• locate the Windows partition;
• read and execute the startup files;
• switch the CPU from "real-mode" to "protected-mode";
• load 32-bit "protected-mode" device drivers for the hard drive, video display, etc.;
• (continue loading Windows).

CPUs always startup in real-mode, so a modern bios may natively include the drivers to handle the first 4 of these steps.  But after the CPU kicks into protected-mode, the system cannot use real-mode drivers.

When you install Windows, the setup routine takes care of that.  The correct protected-mode drivers are extracted from the CD and configured so that when the CPU switches gears, it's got the right drivers to continue accessing the hardware.

A perfect example of this distinction occurs when installing XP on a SATA hard drive.  A modern bios can see SATA (if it couldn't, the hard drive would never boot), but the XP CD doesn't know about SATA so has no protected-mode SATA drivers.  Even though the SATA drive is "visible" when you start the installation process, you have to use the F6 technique to be able to inject the SATA driver from the manufacturer when the setup routine needs it.  If you overlook F6, the setup routine will start, but in the middle of the process the hard drive will suddenly "disappear".

The same issue applies to running XP from a USB drive.  Your bios may be able to see USB devices, and may be capable of booting from them.  But that's because the bios natively has a real-mode USB driver.  When Windows tries to boot, though, the USB device suddenly disappears in the middle of the boot process.  Windows doesn't load a protected-mode USB driver loaded early enough to keep the USB drive visible.

FTR, some people have evidently succeeded in installing XP on a USB drive, but they had to hack the XP installation routine to inject a protected-mode USB driver at the right point in the setup process.  So, it appears it can be done, but the procedure is not for the faint of heart.

Vista has reportedly fixed this XP limitation, and supports installing to a USB device.