Windows 7 is installed on the first 2 partitions (100MB & 250GB) (in BIOS Mode).
Now I want to install Ubuntu 18.04 on the next partition but it doesn't find Windows 7. The installer finds the partitions. If I install it on the empty partition, after finishing I can only boot Ubuntu. If I try it with Ubuntu 16.04 I get a message saying that Windows 7 is installed in BIOS mode, but it wants to install in UEFI, and that then I won't be able to use Windows 7 any more. and so it is.
But why can't Ubuntu also be installed in BIOS mode?