Basically everyone who uses a laptop for producing has this problem, yet somehow none of them are aware of it before they buy one

For future reference, anything built in the ASUS factory is unlikely to have this problem (ASUS manufacture Sony, Apple and... ASUS laptops). I've heard Toshiba Satellite Pro's are also safe, but everything else is a gamble (especially Dell).

First thing to do, is to lower the input sensitivity on your monitors as far as you can handle. Obviously this will limit how loud you can push your speakers, but the lower the sensitivity on the speakers, the louder you can push the signal from your computer (lower noise floor or whatever).
So, with that aside! You have 4 options basically.

1. Buy a good quality generic power supply that won't cause the noise.
2. Get a 3 prong to 2 prong converter (removes the ground completely - ie. if your computer has a spike, the excess voltage will find the nearest ground, which will be your body - you die.)
3. Get a DI box with a ground lift. This is nasty. It's ok for DJing since you only have to worry about what comes through the speakers, but for producing and recording, all that noise will still be in there.
4. Run off battery whenever you gotta do important stuff.

Good luck son.