SI Pro 2.5 was available to download from the developer's website when we last checked. We cannot confirm if there is a free download of this software available. The most popular versions of the program are 2.5, 1.1 and 1.0. We recommend checking the downloaded files with any free antivirus. This tool was originally produced by Fred Miranda. The program lies within Photo & Graphics Tools, more precisely Viewers & Editors.
From the developer:
SI Pro gives photographers access to powerful and flexible options for customizing their own image interpolation outputs.
It is the next generation interpolation tool. This new essential digital darkroom tool features improved algorithms, added options to choose from pre-set and custom paper sizes, pixel dimension, margins, printer resolution and even interpolates your images by scale.
You may want to check out more software, such as BenVista PhotoZoom Pro, Mp3Gain PRO or WinGuard Pro, which might be similar to SI Pro.