Help on Dell Inspiron 9300 sporadic freezing issue

Hey guys...been trying to wrap my head around something for a while but no luck.

I have a Dell Inspiron 9300 which originally had the NVIDIA GeForce 6800 graphics card.  A little while ago it failed on me. Since I dont game much anymore, I decided to just buy a used working pull ATI Radeon X300 from ebay. Plugged it in and installed the latest drivers from Dell website and everything worked fine. PC boots fine and resolutions is as its supposed to be. However, everytime I now use the pc, around 30-40 minutes into using it (e-mail, browsing, normal stuff) the screen freezes on me. Everything gets stuck and just the power light and the HDD light remain on constantly. I cannot do anything except for hard shutdown by keeping power button pressed. 

Below is what I tried:

1) Uninstalling previous NVIDIA drivers and reinstalling ATI X300 drivers (latest ones from  ATI website. Also tried the driver from Dell website). Did not solve.

2) Full format and fresh install of windows. Tried windows XP that came with the system and also tried Windows 7 Home Premium. Did not solve.

3) I have currently disabled the graphics adapter and will see if it still freezes. Maybe it is overheating. However, I dont see that happening as my previous card (NVIDIA GeForce 6800 was more demanding than this little guy...i stepped down!) I will post if disabling graphics card solves this issue or not...which will isolate my problem to the graphics card only.

Also, when I put in this ATI X300 card, along with the new drivers, do I need to update BIOS as well? I did download the ATI BIOS that pops up on Dells website. Is there anything else I need to do BIOS wise?

I also opened up the pc again and made sure  my fans are not jammed or the video card was not installed properly. Everything seems to be fine. I also took out and put back in the RAM cards incase there was static build up or soemthing like that (read about that as a possible cause on some forums so tried it.) No luck.

Was also reading that it could possibly be the capacitors or the PCU. Which capacitors are these? on the motherboard? My mother board was changed by Dell 1.5 years ago so dont think that the capacitors went faulty already...who knows.. Not too sure about PCU as the replacement card was the stock card that was an option while configuring Dell 9300 as well. 

Do you think the motherboard I have is specific for the NVIDIA GeForce card and not the ATI X300 and thats why this issue is popping up?

Any help will be appreciated! Stuck here!

oh i forgot to mention....this problem started happening right after I changed the graphics card.

thanks for the reply.

All I did BIOS wise was download and run the ATI mobility BIOS update that was available on the Dell drivers site. Link is below.

http://support.dell.com/support/downloads/driverslist.aspx?c=us&l=en&s=gen&ServiceTag=&SystemID=INSPIRON%209300&os=WW1&osl=en&catid=&impid=

In the link, if you look under the Video tab, I installed the ATI-BIOS and the ATI-DRIVER. When I installed the ATI-BIOS, it said "this version of BIOS already exists in this computer".

Is there anything else I need to do BIOS wise? I tried doing some googling but couldnt find anything. How do I check for this BIOS update?

ok will try running it in safe mode for a while.

If that solves the problem, what do you suggest I should do?

and

If that does not solve the problem, what do you suggest I should do then?

ok...left the pc on all night on safe mode. Has not froze yet. This is the longest it has gone so safe mode has definately done the trick.

So you think an old driver is at fault here?

I tried googling some updated drivers compared to the one on the Dell website but have no luck.

Can anyone point me to the right direction? 

when you say "my model", do you mean the nvidia graphics card that came with my pc originally or do you mean my pc model inspiron 9300?

Ive done a factory wipe and fresh OS install approx 5 times now, both XP and win7. No luck.

excuse me if I sound stupid, but i didnt get what you mean by the PC model - under windows 7.

a little update :

I formatted and freshly installed windows 7 again. This time I did not download and install any of the suggested driver updates that windows 7 automatically finds....nor did I download and install any of the updates from dell website for my inspiron 9300.

Its been a few hours and pc hasnt froze yet.

Under Device Manager, the display adapter shows "Standard VGA adapter in use".

I will now try installing all updates windows 7 update suggess EXCEPT for the ATI X300 driver it has found for me. It seems to have found the latest one which is:

ATI Technologies Inc. Display Software update released in December 2008.   Published 6/23/2011.

On the dell website, their driver was released in 2005.

Just as a note, I have used this 2008 released driver before with windows 7 and it crashes with it. PC crashes with the dell website 2005 release driver as well. Seems like ive tried every driver there and it still crashes.

Do you think this card is malfunctioning as well?