When trying to upgrade from Vista to Windows 7, upgrade process fails with error message and rolls back to Vista.
Windows failed to load because a critical system driver is missing or corrupt
To resolve this issue perform the following steps:
1. Access Driver Repository Folder under C:\Windows\System32\DriverStore\FileRepository and move any folders that contain the file: iastor.inf to a temporary location.
Note: To move the files from the FileRepostiry you may require additional permissions which can be accomplished by taking ownership of the the folder:
- Right-click on the folder and choose Properties,
- Click Security tab.
- Click Advanced button.
- Click Owner tab.
- Click Edit button.
- Select your account.
2. Search for references to iastor within the oem inf files in the c:\windows\inf folder.
Example Command: findstr /i /c:"iastor" %windir%/inf/oem*.inf
3. Make a note of the oem##.inf files reported where ## is a numeral. Move the oem##.inf and corresponding oem##.pnf from c:\windows\inf folder to a temporary folder.
4. Delete $~bt, $~LS and $~Upgrade folders from c:\ drive if they exist
5. Download and install the latest version of the iastor.sys driver from Intel website on the Vista machine: http://downloadcenter.intel.com/
6. Start the Windows 7 upgrade process. It should complete successfully now.
Note: Once the Upgrade process has completed successfully, there is no need to restore the iastore files, or the oem*.inf and oem*.pnf files back to their original location as the devices will no longer be needed.