New mobo + CPU = problems!

[peode]

Hi everybody!
I recently upgraded my computer. Now I have

mobo: Asus P5N-EM HDMI (before GIGABYTE GA 946GM-DS2)
CPU: C2D E8400 (before E4300)
GPU: 8800GT 512 MB
RAM: 2x1GB
PSU: CHIEFTEC GPS-400AA-101A 400W

evrything boots fine, but I can't play crysis or crysis warhead anymore. I start playing (no matter the settings) and it always crashes very soon - it exits to desktop with a message that "crysis must now close". I downloaded new drivers for everything - sound, GPU, chipset, even a new bios. I reinstalled Crysis, downloaded the demo - doesn't work. I checked the temperatures and everything seems to be normal. I tried playing Far Cry 2 and it worked, even at very high settings, at least for 5 minutes (crysis doesn't even get close to that before crashing). Recently I was watching a video online and the system crashed, I had to reset.

My computer is clearly unstable and everything was fine before. Can anybody hel me?
Thanks in advance.
peode

 

[serpent1202]

My guess would be the PSU isn't supplying enough power to your components. I have a 550W that I had to replace with a PC Power & Cooling silencer 750 when I upgraded to an HD 4850 because when I was gaming, I would get random crashes to the desktop or even sometimes straight reboots. Since the upgrade of the PSU, not a single hiccup.

With that PC I would buy an Antec Earth Watts 650. They are on sale for $69.99 on Newegg right now and they have 3 12v rails. The PCI-E rail runs at 25A which is more than enough to power your card, or any card you'd be looking to be in the near future.

 

[Zorg]

I agree, the first thing to change is the PSU, then see how it goes.

 

[Yoosty]

+1 for serprnt1202 on PSU...

But it could be elated to either your graphic card or cpu, overheating. What Cpu HSF are you using. Plus what brand of graphic card are you using, evga, bfg, xfx??? If it is an evga then go to there site and register on their forum. Then download EVGA Precision, which besides being able to OC the card, it will also let you increase the card Fan speed to keep it cooler. If you have other brand card, then download Riva Turner, it will do the same but is a bit more complicated to use.


Also here is Asus Forum board link for your Motherboard to check out.
http://vip.asus.com/forum/topic.aspx?board_id=1&model=P5N-EM+HDMI&SLanguage=en-us

 

[peode]

Hey, thanks everybody for quick reply!
I already checked how hot everything was and it was ok, iddle or on load.
I guess it must be the psu - I read the GPU manual (finally!) and it read 450W psu recommended.
I have a possibility of buying a 550W Cooler Master. Here are exact specs:
+3.3V 25A
+5V 25A
+12V1 16A
+12V2 16A
-5V 0.8A
-12V 0.8A
+5Vsb 2.0A

You think it's enough?

 

[peode]

.

 

[Zorg]

No the small Cooler Masters are not very good PSUs.

Where are you buying from? Look for a Corsair VX450 or VX550.