Ok, the first question I had concerning the psu, you have answered and the specs on the psu look good. You might try the other psu that you have and see if the problem remains or is corrected.
As to the stop errors you list, you can try going to the Microsoft website and looking up the codes and what they mean. They could point to a hardware error, a driver error, or a software error. Try pulling and reseating the various bits of hardware; cpu, video card, ram, and whatever else there is. After that, try reinstalling all the drivers to insure they are correct.
I notice that you are using a Zalman 9700. Nothing against the Zalman, but if it isn't installed just right, you might be getting a cpu overheat that causes the computer to shut down or reboot. I've had this happen myself and all it took was for me to take everything apart, put on some new paste and put it together again making sure I got all the screws in tight and the Zalman lined up properly. Yes, I felt dumb when I discovered my error, but we all do dumb things from time to time. Anyway, just an idea.
This looks like a device driver issue or faulty hardware. I found the following info on the web for you.
The Stop 0xA message indicates that a kernel-mode process or driver attempted to access a memory location to which it did not have permission, or at a kernel interrupt request level (IRQL) that was too high. A kernel-mode process can access only other processes that have an IRQL lower than, or equal to, its own. This Stop message is typically due to faulty or incompatible hardware or software.
* A Stop 0xA message might occur after installing a faulty device driver, system service, or firmware. If a Stop message lists a driver by name, disable, remove, or roll back the driver to correct the problem. If disabling or removing drivers resolves the issues, contact the manufacturer about a possible update. Using updated software is especially important for multimedia applications, antivirus scanners, and CD mastering tools.
* A Stop 0xA message might also be due to failing or defective hardware. If a Stop message points to a category of devices (video or disk adapters, for example), try removing or replacing the hardware to determine if it is causing the problem.
* If you encounter a Stop 0xA message while upgrading to Windows XPl, the problem might be due to an incompatible driver, system service, virus scanner, or backup. To avoid problems while upgrading, simplify your hardware configuration and remove all third-party device drivers and system services (including virus scanners) prior to running setup. After you have successfully installed Windows XP, contact the hardware manufacturer to obtain compatible updates.
Hope this is helpful. And I think the others suggestion to test with a different PSU is good advice, as lower or in-consistant voltage will make hardware behave differently. Especially when under load.