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I have a really strange problem.

My Network (A) Other Network (B)

1 - When reinstalling XP or Windows 7, Internet Explorer 8 gives a message like: Default Mail Client Is Not Properly Installed network (A)

2 - When connecting this computer to an other provider network (B), this problem does not exist.

3 - When connecting a totally other computer to my providers network (A), the same message appears.

It looks like something in the network/modem/router triggers this event.

Does anyone see any light in the end of the tunnel?

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Check first this article from
Vista could not perform this operation because the default mail client is not properly installed :

Customer recently bought a Vista PC.

After a few weeks he started getting a strange error message:

Could not perform this operation because the default mail client is not properly installed.

This would happen whenever he would click on a mail link within internet explorer.

It didn’t take long for me to realise that there was something wrong with mailto: links on any web page (and also any mailto: link within html emails.

I’m sure there is a setting (or a registry entry), to fix up the mailto: association.

I tried the following steps until it started to work:

  1. Start -> Default Programs -> Set Program access and computer defaults -> Custom -> default email program (you need to scroll down for this) -> set registry values to default.

  2. Control Panel -> Default Programs -> set your default programs -> select windows mail (or your normal email client) -> Choose defaults for this program -> make sure all boxes are ticked (eg .eml, mailto:, email link)

  3. Control Panel -> internet options -> Advanced -> Reset

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