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win7 downgrade to xp pro - unknown disc

datatechdc
datatechdc asked
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i am downgrading my lenovo x100e from win7 home prem to xp pro. i have external usb drive and i start the install of xp pro. however, when it gets to the part where you pick a disc it says unknown disc.

i cant seem to get around this.

help.
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Most Valuable Expert 2013
Commented:
Which disk is unknown?  The CD, Floppy or Hard drive?
To install XP on the x100e you'll need these drivers & Ideally a supported USB floppy disk drive
http://www-307.ibm.com/pc/support/site.wss/document.do?lndocid=MIGR-74324 
Retired
Most Valuable Expert 2013
Top Expert 2009
Commented:
Go into the system BIOS and change the disk access method.    The exact wording depends on the BIOS ... but you basically need to disable AHCI -- usually by setting SATA mode to "legacy" or "IDE", or by simply disabling AHCI.

The XP installer should then see the disk okay.