My laptop freezes while playing games and on power cord

[WantCookies]

So to describe the problem when i play games my laptop freezes but it freezes only when on power cord , when its on battery it does not freeze.
my laptop spec:

Spoiler

Acer Aspire 5542G

Windows 7 Ultimate x64

CPU Type Mobile DualCore AMD Athlon II M320, 2127 MHz (10.5 x 203)
Motherboard Name Acer Aspire 5542
Motherboard Chipset AMD 760G/780G/780V/785G/790GX/880G/890GX, AMD K10
System Memory 4096 MB (DDR2-800 DDR2 SDRAM)
DIMM1: SK Hynix HYMP125S64CP8-S6 2 GB DDR2-800 DDR2 SDRAM (6-6-6-18 @ 400 MHz) (5-5-5-15 @ 333 MHz) (4-4-4-12 @ 266 MHz)
DIMM2: SK Hynix HYMP125S64CP8-S6 2 GB DDR2-800 DDR2 SDRAM (6-6-6-18 @ 400 MHz) (5-5-5-15 @ 333 MHz) (4-4-4-12 @ 266 MHz)
BIOS Type Phoenix (01/18/10)

Display
Video Adapter ATI Mobility Radeon HD 4500/5100 Series (512 MB)

The things i rule out:
Overheating: I've monitored the tempteratures on the CPU - 70 degrees max
Freshly installed Windows 7 x64 , all drivers up to date ( the video driver aswell )
The thermal paste is changed , the fan is clean
The AC charger is new ( not an original one but it worked fine a few months )
and i just dont know what can cause this

 

[Tom Tancredi]

It is obvious, the 'new' AC Charger outputs power enough for 2D (icons, Word, Internet Explorer) but isn't the correct FULL power amount enough when the 3D part of the videocard kicks in (requires more energy to generate the 3D graphics in games, etc.). You should seek out the OEM version instead of whatever this one is.

 

[WantCookies]

i forgot to say that i've played games with that same AC adapter before i dont know what might have changed , i tried another ac adapter from an acer laptop and it did the same thing

 

[Tom Tancredi]

Take out the AC adapter. Take out the battery. Plug in the AC Adapter only. Try to game: does it work now?
If it does it means your battery is bad and is causing power interference. Batteries should be REMOVED from laptops ALL the time your just using it as a PLUGGED IN DESKTOP replacement, or else you OVERcharge the battery and wear it out faster. You should plug in the battery to 'CHARGE' the day before you plan to 'travel' with the laptop (even if it is out to the backyard), but then again unplug it when your 'back to your desk'.

IF it does NOT still work, I said get the OEM adapter, that means the specific make, model, and POWER type for THAT Acer Aspire 5542G, not just 'any Acer' power supply. You can have different power requirements from similiar make / models (Acer Aspire 5541G vs your 542G), I seen it weirdly happen occassionally. If you have the EXACT same type power output (you checked the wattage, volts, amps) of the OEM and your STILL having the problem with no battery in, then your PC is damaged and will eventually fail to power on at all.

 

[WantCookies]

soo the problem was with one of my ram sockets, because im playing a second game of dota 2 with only 1 piece of ram and it does not freeze