I have used Roots3 since 1990.It's great!Unfortunately, I now have the same problem as you "Insufficient memory, class 8, at 17640.
I can't fix my own problem, but feel absolutely positive the answers lie in correcting or adding to config.sys and autoexec.bat files.
I have 44,000 in my database & was running without trouble until a month ago.At the first sign of trouble, my computer insisted I had to run set-up again.I did, but then later learned whild doing a backup that some files would not backup.Still later, my database was corrupted, & now I can't open the database either.
If we find a DOS expert, I'm sure both of us will be O.K.Too bad Howard Nurse & his original tech staff at Roots3 are not available.They were wonderful!!
Stay in touch.If you get the solution first let me know, I will do likewise.