If you want to open an OLM file in Windows, you can convert it to PST format and then import it into the MS Outlook application. There are several free desktop applications that you can use to perform OLM to PST conversion. CubexSoft OLM Export is a good one as it lets you convert OLM to a lot of file formats including PST. It also lets you convert OLM to document formats like PDF and RTF. So, you can convert OLM to these document files and view the content of OLM email files on Windows.