Colonel:
I think I see your problem. And I can lead you there, but I'm not going to make the final decisions for you. Enough said about that.
The first line in the Softmenu III Setup is CPU Operating Speed. If you click "enter" while it's highlighted, and "User Define" appears, select that and hit enter.
The next line down will be CPU FSB. If you're going to try running a 160 fsb, then after you enter that dec number, and hit enter again,
Two lines down you'll have to run about a 10X multiplier to end up with your 1.6 Ghz, for a 1900.
After you've entered your multiplier, and hit enter again, the next line up wil be your Ratio settings ~ {FSB:AGP

CI}.
Just to confirm your CPU, with a 5:2:1 split your resultant AGP/PCI freqs. would then be 64/32; with a 4:2:1 split your resultant AGP/PCI freqs. would be 80/40. So I suppose you can see where this is going.
What it occurs to me you were doing was upping your FSB without adjusting your Multiplier. Is that what was happening?
If you can actually reach a 166 FSB, and I'm not saying you can on that board, but who knows, you'd have to run a 9.5 Multiplier to get about 1577 on the CPU. A 5:2:1 split would then give you AGP/PCI of 66/33 ~ that's why you can run PC2700 mem on that board, basically, because of the KT333 chip ~ and a 4:2:1 split would give you, of course, 83/41.5 other buses.
I dont know what peripheral cards, or memory you're running, but can they take that!? Good question, right?
There's a gap between all those wonderful lines we were just discussing and the next set of lines in the SMIII setup menu. They're the CPU Power Supply, which is probably on CPU Default...
If you hit enter when CPU Default is highlighted, all kinds of new options are going to open up to you ~{Core Voltage, I/O Voltage, and DDR Voltage}, when you exit the CPU Power Supply setting screen. But in the CPU Power Supply screen, again you need to select User Define. Is it starting to come together for you now?
Whoops! My daughter's calling me. Gotta run for a few.
Ok, I'm back. Moving on... Right under the Multiplier Factor, on the same SMIII screen, there's a setting called Speed Error Hold. It is selectable as either Disabled, which is the default, or Enabled. If it's enabled, and the CPU speed setting is wrong, the system will hold.
If you've commited an invalid clock setup, you wont be able to boot, but then you've got a couple of options...just in case you're having trouble getting back into BIOS. Well, yeah, you can split the case and reset the CMOS. Ok, that's one...but there's another.
If you just press the INSERT key (assuming you've enabled USB keyboard support in that erroneous BIOS, of course) when powering on, the system will revert to it's standard parameters so you can reenter the BIOS again (given appropriate followup keystrokes) and make changes. If that's annoying, maybe you're just like me anyway, and the side of your case is already off. Just kill the CMOS and start over.
Is or has any of this been of real use to you, at clearing things up?