I have just (finally) got Twinview to work on my Mandrake 9.0 system. For info, my system is;
Asus P4Pe with P4 2.4b running at 2.92 Ghz.
1G PC2700 RAM
Nvidia Geforce 4 Ti 4600
Monitor 1; Samsung SynMaster 955b CRT
Monitor 2; Hitach CML174SXW LCD
Mandrake 9.0 Kernel 2.4.19-16mdk
XFree86 4.2.1, patch level 3mdk
Nvidia Driver 4191
At the minute the desktop is "Stretched" across the two monitors,so my next task is to find a way to make it look a wee bit better. Also, when I start Tuxrace, it is split across the two monitors (although it is actually running smoothly).
I have attached a copy of my XF86Config-4 file for you to look at - maybe it will help.