You've got a couple of potential problems. The buzzing sound inidicates a fault, but you know that already. The question is... Why?
1) Your 150w inverter is likely not able to supply enough power for the laptop. It's a pretty high-end laptop. For a laptop installation, you're a lot better off with a DC-DC "car adapter" for the laptop for a lot of reasons discussed elsewhere on this forum.
2) Your inverter is connected to a cigarette lighter/power port in your vehicle. More often than not, these auxilliary power ports aren't able to supply the amount of power due to the wiring for that power port. I ran into this problem when I was first putting my setup in my truck. When I powered the system throught eh cigarette lighter, it simply would not work. When I wired it directly to the battery, the problem went away.
3) Your inverter could be faulty or just a piece of crap. If this is the problem, you have two options: replace the inverter or get a DC-DC adapter for your laptop. I recommend the latter.