Adobe files not opening error in new version (from AI2 or CS5 into CS6)

Adobe files not opening in new version - Error : File not found

Reason : File or ,& folder name may contain foreign non-English characters

Test : Move one of your files into a folder with English characters &change the file name into an English name, if not. if it worked, then let's change it from Windows as follow:

1. from the Windows Control Panel

2. change the option:

"Language for non-Unicode programs" and choose the language that your folders or file names is in.

3. Restart the computer 

4. it works

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 Then to change the fonts within the Illustrator all at once

the easiest way is to use the Type > Find Font command and change all instances of one font into another. If you did use Paragraph Styles or Character Styles you can turn on Redefine Style When Changing All.