Optimal usually isn't the highest it can, it can be a couple of settings below this on occasion.
Check what the max refresh rate is for your monitor at that resolution and then alter it to something below that.
i.e: if you monitor supports 110hz maximum at 1024x768 and then supports 100hz, 85hz 75hz etc.
Optimal probably has it running at 85hz, which is fine but if you want to jack it up, why not go for 100hz, that way it's even crisper without overstraining things.
nb: w2k shouldn't allow you to overstrain your monitor....usuaully