The quest for ever increasing download speed is like a quest for the holy grail and HiDownload attempts to reach nirvana through mutli-threading.
HiDownload is basically a multi-threaded download manager that allows you to download individual files (or lists of files) from web and FTP sites to get the most out of your broadband or dial-up connection. The program supports multimedia streaming with all important pause and resume features which allow you to download movies, music and capture streaming video at your own pace or to avoid disappointment if you suffer a broken connection. In addition, it provides all the standard features of a download manager, including scheduling, a drop basket, download history, clipboard monitoring, download categories as well as zip previews and more. To look at, the interface is nothing special but it does clearly display your current downloads plus a browser window in the left hand pane from where you can locate files on your hard drive. The big question is, does it really speed-up downloads then? Well, as an alternative download manager for either IE or Firefox, it's certainly a better option giving you much greater control over how your downloads work. However, the actual speed differences are negligible and depend greatly on the state of your connection and that of the server delivering the file.
As an alternative download manager for your browser, HiDownload is a decent choice but don't expect it to perform miracles on your download speeds.