This is due to the MP3 Add On not being supported on Windows Vista.
You can find the minimum system requirements for the Add On here:
https://shop.presonus.com/products/software/studio-one-add-ons/MP3-Converter-for-Studio-One-Artist
For PreSonus Studio One Artist (version 2.6.2 and higher)
MAC
- Mac® OS X 10.7.2 or later
- Intel® Core™ Duo processor (Intel Core 2 Duo or Core i3 or better recommended)
- 2 GB RAM (4 GB or more recommended)
Windows
- Windows® 7 x64/x86 SP1, Windows 8 x64/x86
- Intel Core Duo or AMD Athlon™ X2 processor (Intel Core 2 Duo or AMD Athlon X4 or better recommended)
- 2 GB RAM (4 GB or more recommended)
Mac and Windows systems
- Internet connection
- Monitor with 1280x768 resolution
- 2.5 GB hard-drive space for Stereo Loops
- 20 GB hard-drive space for Multitrack Loops
- 23 GB hard-drive space for Complete Acoustic Drum Loop Bundle
