Downloading PM100 4.0 from the developer's website was possible when we last checked. We cannot confirm if there is a free download of this software available. The actual developer of the free program is Thorlabs GmbH.
According to the results of the Google Safe Browsing check, the developer's site is safe. Despite this, we recommend checking the downloaded files with any free antivirus software. The most popular version of the tool is 4.0. The most frequent installation filename for the software is: PM100.exe. The software relates to System Utilities.
From the developer:
The PM100USB comes with an utility software that easily enables remotely operating the PM100USB and visualizing and logging measurement data. The software is written in LabVIEW 8.5.1 and can either be installed from the data carrier as executable where LabVIEW isn‟t required on the PC; or can be run with LabVIEW 8.5.1 or higher.
You may want to check out more software, such as PM100-PM200 Utility, which might be similar to PM100.