I have a new mobo and power supply.

When plugged in with the external power supply (battery charger), my laptop goes crazy. Sometimes the fan becomes really loud and then the laptop dies.
My USB keyboard and mouse is noticeably laggy. It wont die if i play power hungry games. The fan periodically turns on and off, and i found it strange since it doesn't do this before.

These problems doesn't occur when im using the battery power.

Try another AC adapter

New update...

I noticed that i have a emachines 6xxx motherboard on my gateway notebook. I researched it and it might be the same mobo yet different BIOS version. Maybe thats why they gave me another power supply.