The latest version is SpeedFan 4.50. Some tools (like Norton Internet Security or ZoneAlarm) may interfere with the download process. Basically, the REFERER field must be properly sent to SpeedFan's web server. Download won't work if any tool blocks it.
For webmasters: if you do not want to mirror the download locally to your website, please link to
https://www.almico.com/speedfan.php and not to the direct download as it won't work. Thank you for your cooperation.