Adobe Illustrator

here's a link to the Adobe Illustrator help page though in case you need it later:
Edit [Moderator]: Link removed

Also you can try:
1. Close Adobe Illustrator.

2. Right-click on the Windows "Start" button, and click "Open Windows Explorer, then the file manager opens. Navigate to the AI file to delete.

3. Right-click on the AI file to show the context menu.

4. Click the "Properties" option. The Properties dialog box opens.

5. Uncheck (clear) the checkbox next to the "Read Only" option in the File Attributes section.

6. Click "OK," and close the Properties dialog box.

7. Right-click on the AI file, and click "Delete" from the context menu. Click "OK" to confirm the deletion. The AI file is deleted.

Good Luck!

< Open the AI file you want to repair.

< Choose "Object" and then choose "Path."

< Choose "Cleanup." (Note: Empty text paths, stray points and unpainted objects will be deleted.)

< Choose "Paste Remembers Layers" only if your AI file contains multiple layers. (Note: This option is available from the Layers Panel menu.)

< Drag a marquee around all of your artwork in the file by using the Selection tool.

< Choose "Edit," "Copy," and then choose "File."

< Choose "New," "Edit," and then choose "Paste in Front." (Note: "Paste in Front" will place your artwork will mirror the damaged AI files).

< Choose "File" and then choose "Save." If your file is still damaged, continue.

< Make a copy of the file and give it the same name except add the "C1" to the end of the title. (Note: You can choose any other letter, number or other word to differentiate it from other versions.)

< Open the first copy version, select one art object within the file, and then delete it.

< Save the file and add a number "C2" at the end of title to differentiate it from other copies and then reopen the file. If your file is still damaged, continue.

< Repeat steps 10 and 11 until you can identify the object that is causing the problem.

< Delete the damaged object when you find it and then re-create it by using either the drawing tools, reestablishing a link, or by changing or replacing the font of damaged text.

Also see more info on this Microsoft site: Edit [Moderator]: Link removed