Acer Aspire Freezes Randomly, Tried Everything

I Have an Acer Aspire 3050 that freezes occasionally and can not resolve this issue. When it locks up, nothing works (ctrl alt delete, power button, mouse..ect)
I believe I tried almost everything.
When it freezes, the only way to shut it off is to pull the battery out. I tried holding the power button for 5 seconds to no result.
I also replaced the ram, formated the drive and reinstalled both windows xp, and vista, replaced the hard drive, opend up the laptop to see if any dust was on the fans blocking heat dissepation....it is clean. I removed the Wi-Fi controller just incase, still the same.
The CPU fan still functions and its temperature is at a normal 50 degrees.

What else can I try?

It is and AMD Sempron 3500
512mb ddr2 ram pc 5300
80gb sata drive (also extra 160 drive i tried as well)

Please help me!!

 

have you ever go to your bios and takes standby..while you;re in bios setup.have you notise also freezing? if so..try clean your processor. if your processor is detachable better clean..and also you whole motherboard... clean it with a tinner...
good luck

 

evn i had the same model , Acer Aspire 3050 and it use to hv the same proplem like your.. when i am in middle of somethin it would just get stuck n then i utimately would have to switch off the power.. i then gave it to the company itself cause i dint want to try anythin on my own.. why dont even u do tht...