I recall at one time installing Windows 98SE fine on a USB HD, but XP just won't. When i try to install XP Pro x64 it gives me a BSOD after copying files in the 1st section of setup that says; "UNMOUNTABLE_BOOT_VOLUME" What gives? Why does this happen? I found a guide here that tells me what to do. But, although i haven't tried it yet, it requires to burn a new copy of XP CD. Can I modify the contents of the XP CD from the USB HD and install from there? I'm using a Western Digital Passport 120 GB, and my BIOS fully supports booting from USB, it's listed as 'USB Device.' Some help would be great.

Thanks in advance.

If you want to install XP from a usb hdd, please use the usb_multiboot(7).cmd

http://www.msfn.org/board/install-XP-USB-t111406.html

Unfortunately you can't install XP x64 from a USB HDD because during the install process we need to use a driver (rdummy.sys) which tricks setup in thinking that the usb hdd is a removable disk and this driver has not yet been written for 64bit.

Your should be able to use the above mentioned program to install x64 from a normal usb flash drive.

rdummy.sys? What a retarded name! Actually, i want to install XP x64 to the USB HDD NOT install it on a regular HD from the USB HDD. Of course, this would entail booting from the USB HD. So far, i haven't had time to copy and modify the contents of the CD on the USB Hd and install from there. I'll post back as soon as i do that.....

Thank you, nice start
I guess the author of dummydisk.sys should also be pleased, as rdummy.sys stands for reverse-dummydisk.sys. But that's not interesting matter.

If I had to follow your lines, I'd have to write something like "what a retarder question in this forum, don't you read forum names? And lastly- don't you know about google.com...or forum's search option..."

But since it's a friendly forum, I will point you to some of the answers:
Where it all started:
http://www.911cd.net/forums//index.php?showtopic=14181

In Dietmar's signature you will find links to his guides.

Some variation, all based on Dietmar's work:
http://www.911cd.net/forums//index.php?showtopic=16760
http://www.911cd.net/forums//index.php?showtopic=16696
http://www.ngine.de/index.jsp?pageid=4176
http://www.usboot.org/tiki-index.php <---this might not work for x64

I don't remember reports for using XP x64, but don't think there should be any difference, apart from the mentioned one above.

ilko