I’m currently trying to install Magento Community 1.7 on Windows following the instructions given in the Magento Community 1.7
1. Open php.ini in notepad.
2. Locate Dynamic Extensions Section.
3. Remove semi-colon from the beginning of each instruction referring to the PHP extension throwing the error.
4. Save and exit.
5. Stop and Re-start Apache Web Server.
6. Re-validate in the downloader.
Hope this helps.
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