Success!
Bushfiva - input of DVD media from video_ts + VOB worked perfectly. Thanks!
Third party conversion freeware took some searching - lots of red herrings.
This link
WinX Free FLV to WMV Converter - Free Convert FLV Video to WMV is the first to work OK, without apparent limitations and is freeware (thus far). I need to download a long test flv file; some of the downloaded converters limited conversion to a fraction of the file. So far, so good, though.
This conversion freeware might be useful for others, whether SONY Vegas Movie Studio users or not.
Many thanks, everyone!
