I highly recommend the free, small utility from ASoft, that allows you to determine what Microsoft .NET versions are installed on your Windows computer.
BNW, check your PMs
http://www.asoft.be/prod_netver.html
'Napper required only the 3.5 Framework. 'Ripper needs the v4.1 Framework, and afaik the latest 'Ripper versions are 64-bit#.
It's easy to download and install the .NET Framework v4.1 or v4.2 (effectively equivalent), and this won't cause any other programs on your Windows computer to misbehave.
#My guess is that a lot of ppl will need a 32-bit version.