NLE Workstation Sudden Shutdowns - CPU Temp?

Hi, thanks for any help in advance.

We use this system solely for DV editing and encoding, burning DVDs. Lately it has taken to shutting off without warning while it is processing (encoding, rendering). I checked the CPU temp in the bios after such a crash and the temp was above 150 F. I don't know if that is auto shutdown territory or not. It does seem to only happen when there is a load(50%+ sustained) on the cpu.

Should I assume heat is the culprit here? If not, what else might cause these symptoms?

In an attempt to finish a project which had crashed the system on several attempts, I encoded and burned a DVD with the side panel off of the tower. This time the system made it through without dying.

3.4ghz P4 Prescott socket 478
Stock Heat sink & Fan
MSI Neo2 Board
1bg dual channel pc3200 ddr memory
1 120gb ide system drive + 2x 160gb Sata drive for storage. Often have a Seagate USB2 400gb 7200rpm drive attached.
Radeon 9550
DVraptor RT2Max w/ Adobe Premiere 1.5 for RT DV editing

It sounds like heat is the direct or indirect culprit. Here are some possibilities:

1) Dust bunnies have accumulated in the heatsink of the CPU cooler, inside the power supply, and/or elsewhere. Use a compressed gas duster can (from e.g. Officemax) to blow all the dust out of the case (don't try to stick a vacuum cleaner nozzle inside as static/mechanical damage may be a problem).

2) A fan may have failed. There should be a fan built into the CPU cooler. There should be one or two fans built into the power supply. There should be at least one fan at the back of the case blowing outward. Are all of them still working?

3) The thermal compound ("goop" ) insuring good heat flow from the CPU to the CPU cooler may have dried out and no longer be working properly.

4) Power supplies slowly "wear out" over time, producing less power. They also produce less power at higher temps. Since you didn't list the brand and model number of your power supply, I'm guessing it's a no-name/el cheapo that came with the case. Such a power supply is most likely low quality and thus more prone to this drop in output over time.

Thus, here is what I'd suggest:
a) Blow out all the dust with a can of compressed gas.
b) With the side panel off, check to see if all the fans are working; if not, replace the fan or fan-containing component.
c) Buy a small syringe of Arctic Silver 5 thermal compound (widely available at stores like CompUSA and probably even Best Buy and Radio Shack as well as mail order at newegg.com etc for $10 or less). Buy some "anhydrous isopropyl alcohol" at your local pharmacy/supermarket for $1-2.
Carefully remove the CPU cooler, leaving the CPU installed on the MB. Using the isopropyl alcohol, clean the remnant goop off the cooler. Next, carefully clean the remnant goop off the top of the CPU. See step 2.5 onward in this post for more info: http://forumz.tomshardware.com/har [...] 72#1184072
Apply a grain-of-rice sized dab of Arctic Silver 5 to the middle of the top of the CPU, and reinstall the CPU cooler.

Hopefully, the above will fix your problem. If not, buy a new good-quality power supply and install it in place of your current one. Here are some options:
A) (budget) FSP Group (Fortron Source) FSP400-60THN-R ATX 400W, PCI Express Power Supply - Retail. $50 + shipping from newegg.com.
B) (good, likely can be used in your next computer, too) OCZ StealthXStream OCZ600SXS ATX12V / EPS12V 600W Power Supply 100 - 240 V CB, CE, CSA, UL, FCC - Retail. $85 + shipping after rebate from newegg.com.
C) (quite good, can be used in your next computer, too) CORSAIR CMPSU-520HX ATX12V v2.2 and EPS12V 2.91 520W Power Supply 100 - 240 V UL, CUL, CE, CB, FCC Class B, TUV, CCC, C-tick - Retail. $115 after rebate, free shipping from newegg.com.