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Warning! Any attempt to reinstall Windows ME may make the machine completely unusable or the data unrecoverable!
The best method to recover data is to slave the drive to another computer, internally or externally and retreive the files to a stable system!
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O.K. if you still want to try re-installing Windows ME anyway:
The Windows 9X (98 or ME) installed by Brand name companies (and many whitebox/clone distributors) usually included the complete installation files in C:\Windows\Options\Cabs.The directory location may vary but this was the most common.
For the better known brands such as Dell and HP this folder also included the drivers required for the hardware of the specific machine.
If this foldler exists, copy it and any subfolders to a CDROM or USB device if you can. (Standard warning to ALWAYS back up before you try to fix things).
If the folder DOES exist and you can boot to DOS mode, you can run the setup from the command prompt!
Before running setup, I would run scandisk or chkdsk /f on the drive.
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AGAIN SEE WARNING ABOVE.
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Verify where your current windows directory is.
C:\WINDOWS
C:\WINME
C:\?????????
At the prompt. C:>
cd windows
cd options
cd cabs
setup
Setup will run and will perform a Quick Scandisk. (basically just check that the directory structure is intact)
Setup will see the existing installation and offer to install windows in another directory. Usually WINDOWS.000.
Change this directory to point to the existing installation of windows.
Windows will perform a re-installation over top of your current windows.
For more information try google for more detailed instructions on re-installing Windows 98/ME and the issues you may run into.