[TYPO3] backup; extension cannot be fetched

[Albert Dekker]

I try to install one of the backup extensions on a local installation 
(localhost)
The extension is not loaded with the following comment:

"Error: The datatransfer did not succeed. The T3X file could not be 
fetched. Possible reasons: network problems, allow_url_fopen is off, 
curl is not enabled in Install tool"

DoIdo anything wrong?

Thanks,
Albert