The old version of RealPlayer Version 1.1.5 couldn't do a MKV to RMVB conversion.
I downloaded a newer version form 2 different software download sites.
Both were unknown to me. I scanned the .exes which were actually downloaders instead of the actual program installer. MalwareBytes found malware in both.
So I gave up on getting a newer version.
I know some of my paid converters will do this but I thought a free one might be in order. I had an older version of FormatFactory & it wouldn't do this conversion. So I downloaded the latest version. It also came with a downloader but this one scanned clean. I used it
Watchout for all the "crapware" it wants to install
"Decline" all of it.
At that point the FFSetup184.108.40.206.exe will be in the same folder as the "downloader".
Install from that. Uncheck & Decline the "crapware" that is offered again.
This is where I turn FormatFactory into a portable(almost).
I copy & paste FF's folder from Program Files to another location.
I then uninstall FF .
Then just use the .exe from the copied folder.
This is where the "almost" comes in.
FF will ask & need to install some "inside codecs" & the avisynth it wants.
These appear to be installed in the copied folder. But there may be some registry settings made. I didn't monitor those.
FormatFactory isn't my favorite converter but it will work or seems to be as the conversion isn't finished yet.