Unmountable boot volume. This error can occur during some Windows XP installations. Unfortunately, it can lead to a situation where you can't boot Windows XP, nor can you easily uninstall Windows XP and revert to your old operating system (e.g., Windows 98 or Me, etc.).
Some people find that updating the BIOS fixes this problem; others find that disabling Ultra DMA, but leaving PIO enabled solves the issue (but slows down the system's disk performance substantially). Still others see problems after trying all of the above, as well as more Draconian (and usually ineffectual) fixes such as reformatting, replacing the master boot record (MBR), running the XP "fixboot" utility, etc., etc.
As it turns out, Microsoft calls the problem a feature "by design" and claims the purpose of this behavior is to prevent potential data loss due to the usage of an incorrect IDE cable for the faster UDMA modes.
This behavior may occur if the following conditions exist:
You are using an Ultra Direct Memory Access (UDMA) controller with your computer.
You are using a standard 40-wire connector cable to connect the UDMA drive to the controller instead of the required 80-wire, 40-pin cable.
The basic input/output system (BIOS) is set to force the faster UDMA modes.
To resolve this behavior, Microsoft recommends replacing the 40-wire cable with an 80-wire UDMA cable,
-or-
Try loading the 'Fail-Safe' BIOS default and reactivate the most currently used options such as USB Support.
For further reading, see Microsoft's KnowledgeBase article Q297185
"STOP 0x000000ED UNMOUNTABLE_BOOT_VOLUME" Error Message During Windows XP Upgrade (Q297185) ---- (Q297185)
Excerpt from this page:You may receive the following error message when you first restart your computer during the upgrade to Windows XP
size 6532 bytes, updated 10/25/2001 9:24:00 PM GMT)
After wading through a vast number of reports, it seems this problem happens most frequently when using AMI BIOSes and VIA chipsets (the latter has been on our "evil hardware" list for most of the last two years). VIA chipsets are well known to suffer from a number of shortcomings, not the least of which is a dependence on the so-called "4 in 1" drivers to enable high performance drive access. It appears these drivers may be an issue here, too.
In general, the best way to install these drivers is to download the newest version (using a different computer if your primary PC is incapacitated) from the VIA website, then install them as noted below and reboot. If this is not possible, you'll find older versions of the VIA 4-in-1 drivers on your motherboard CD.
To install 4-in-1 drivers
a) Extract and Save the drivers on a floppy diskette.
b) Near the start of the Windows XP installation routine, the system prompts you to Press F6 to install other drivers. Press F6, then insert the floppy to install the drivers. Windows XP, like Windows 2000, recognizes the drivers as SCSI -- this is normal. With any luck, your installation should then proceed without a hitch.
Our long-term suggestion is to avoid VIA as the maker of your next motherboard's chipset.
