Hello,
You still need to select a video mode that is capable of configuring
the correct frequencies for use with a PC/VGA monitor. Try multiscan, DBLPAL,
DBLNTSC or "Euro 72". If you're still having problems, try using the "VGAOnly"
patch (it needs to be in devs:monitors, you may find it in storage/monitors).
For old games and the like, your best bet is a "scandoubler"...that will convert
the standard amiga display frequencies into something compatible with a
VGA monitor.