How to change privacy of Facebook wall posts already made?

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I made a facebook wall post to friends only but now i decided that i want everyone to see it but when i press the lock icon next to the post nothing happens? Is it possible to change the privacy of a facebook wall post already made?
If i re add or post it again will the comments people wrote on my post also appear after i re add it. How do you re add it or post the same wall post again?

[ITS2011]

Delete them and readd them with the new settings applied or possibily change the global account settings to prevent anyone other than friends from accessing your wall.

[Bi Bi]

Delete and post again

[anonymous]

Change the privacy options, then Delete & repost them.

[Steve]

No, you can't change this after the fact. Here are links to the latest privacy settings for Facebook.
http://blog.facebook.com/blog.php?post=391922327130