'bad checksum, error 251' @ POST

[KarmicApexIntel]

OK please bear with me guys, as this problem description might seem a little long, but nevertheless I think it's relevant to the current issue I'm having..........
Alright here we go...I own an eMachines T2385 desktop PC (w/ about 750MB RAM installed), which not long ago unfortunately fell victim to yet another one of those infamous Bestec 250W PSUs going south and subsequently taking my motherboard with it, which was the following model & specs, etc etc:
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Trigem Imperial GLVE
Processor Brand: Intel
Processor Socket Type: mPGA478
Processor Family: Pentium 4 (Northwood, Willamette)
Maximum Processor Core Frequency: >=2.2 GHz Northwood; 2.0G Hz Willamette
Processor Front Side Bus Frequency: 400/533 MHz

Chipset***
Chipset: Intel 82845GL / 82801DB / 82802AB
Chipset "North Bridge" and Revision: Brookdale-GL GMCH
Chipset "South Bridge" and Revision: ICH4
Super I/O: SMsC LPC47M102
Flash BIOS Device: FWH 4 Mbit
IDE/ATAPI UDMA Modes: ATA-100/66/33

Intel® 82845GL Graphics Memory Controller Hub (GMCH)
Processor/Host bus support
Integrated DRAM controller
Integrated graphics AC ‘97 controller
Integrated 3D/2D graphics accelerator
Integrated 350 MHz RAMDAC
Arithmetic stretch blitter video
Power management functions

Intel® 82801DB I/O Controller Hub (ICH4)
Support for the PCI interface
Integrated IDE controller
USB 2.0 and DMA controller
Power management logic
Real-time clock
Support for AC ‘97 audio devices

Intel® 82802AB Firmware Hub (FWH)
Firmware Hub (FWH) interface

Memory
Memory Type: Unbuffered DDR Synchronous DRAM (DDR SDRAM)
Memory Speed: PC2100/PC1600
Memory Sockets: Two 184-pin 2.5 V DIMM sockets
Maximum Memory: 2 GB
256Mbit Memory Support: Yes
Front Side Bus: 400MHz

Audio
Onboard Audio Configuration: Intel ICH AC 97 CODEC
AC'97 Codec Device: AD1886
Audio Jacks: M, LI, LO, (Header)
M Microphone
LI Line In
LO Line out
SO Speaker
CD-In Connector: 1
Internal Spkr-Out/Line-Out/Headphone-Out/Mic-In Header: Yes

Video
Intel: Extreme Graphics (845) AGP
Manufacturer: Intel
Bus: AGP
Chipset: Intel 845
Video RAM Type: Uses system memory
Video RAM Size: either 1-16MB or 1-32MB (Shared memory architecture similar to the Intel 810/810e chipset)

Onboard I/O Connectors
USB Interface Specification (2.0/1.1): USB 2.0
USB Ports (Front): 2
USB Ports (Rear): 4
(1) DB-9 Serial Port
(1) DB-25 Parallel Port
(1) PS/2 Keyboard Port
(1) PS/2 Mouse Port
(1) Microphone Ports (Back)
(1) Audio/Line In Ports (Back)
(1) Spk./Headph. Ports (Front)
(1) Spk./Headph. Ports (Back)

Onboard IDE
• N/A

Expansion Slots
3 PCI v2.1

BIOS
System BIOS Core Brand: Phoenix

Onboard LAN
Onboard 10/100Mbps Ethernet LAN Supplier: Realtek RTL8100(B)
Ethernet Configuration: Down(PCI)
Wake-on-LAN, Wake-on-Ring: via PME#(PCI)

Protection and Management
Fan Headers (CPU, System, PowerSupply) CPU,System,Power
CPU Fan Speed Control (for active fansink): Yes
System Fan Speed Control: 50%/NA/100%
CPU Fan Fault Detection (fan RPM check): Yes
Onboard DIP Switches and Jumpers Functionality: N/A
ACPI Standby States (S1, S3/STR, S4/Hibernate): S1,S3,S4
ACPI Specification Compliance: ACPI 1.0 ver 1.0 b
IOAPIC Support: Yes

Environmental Requirements
Temperature
- Operation : +5°C to 35°C
- Storage : -10°C to 55°C
Humidity
- Operation : 30% to 80% (No condensation)
- Storage : 20% to 90%

Form Factor
micro ATX
245mm x 230mm x 1.6T (4 Layers)
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Now, the only upside of the PSU failing, was that it at least it still left my RAM memory, my CPU, and my hard drive intact.
Luckily I have a buddy who happened to have another Trigem Imperial GLVE laying around unused, and he was kind enough to give it to me. At the time I didn't have any spare cash to spare for buying a new PSU for the pc, so after I installed the 2nd mobo, another friend brought me by a spare 350W PSU of his to borrow overnight, just so I could temporarily use it to see if the new mobo indeed worked or not. It did, and after Windows XP finished booting, I allowed it to re-install all the mobo-related drivers again, etc etc, then allowed it to reboot again, and everything was fine. So I unplugged my pc, took out & gave back my friend's PSU, and waited til I could afford the spare cashola to go buy a new PSU...

Now to the actual problem I am having: This weekend I bought a new 350W PSU for it, installed it and it booted up once but froze barely after finishing loading up to the desktop .
Obviously I then had to manually unplug it & then cold-boot it, and this time it froze up at the WIndows XP logo boot screen. So I cold-booted it again, and this time I also went into my BIOS settings just to make sure everything was normally set & all that and all that (which it was), and then I exited without changes, rebooted again and THIS time, the front power up light came on, the front lights on both of my optical drives came on, but the screen never did anything but remain black, no BIOS screen, and it never did a POST either. Tried to reboot three more times, with the same outcome. Next I unplugged my pc, and first I pulled out the CMOS battery and tested it across a meter to make sure it was still good. It was. Reinstalled that back in its socket, and next I moved the jumper on J4 for about 5 minutes to enable clearing the CMOS, then moved it back. This time I was able to get into the BIOS settings, but as I was going through it, the pc actually froze IN the BIOS settings windows, which I'd never seen happen before w/ anyone. I cold-booted again, and this time I got an error message saying 'bad checksum, error 251'...Since then, regardless of whether I clear the CMOS again or not, it did what I described before where I had only a black screen on my monitor, despite all other lights and things seemingly appearing to be starting the boot process....Oh yeah and btw, both the PSU and CPU fans are working fine every time too, and I even inspected and made sure the CPU's heatsink still had the proper amount heatsink compound on it, which it did...
SO..........does anyone here have any ideas as to what might have caused this to occur? Sorry for so long of a post, btw....

 

[mailpup]

It might be a bad power supply even though it is new. What is the brand and model? I hope you weren't trying to save money by buying a real cheapo.

 

[KarmicApexIntel]

It might be a bad power supply even though it is new. What is the brand and model? I hope you weren't trying to save money by buying a real cheapo.

I'm trying to remember the brand, but I can't think of it 'cause I'm @ work and not home at the moment.....but no it wasn't a cheapo; I'd call it moderate....after my experience with that crappy Bestec 250W psu (which eMachines saw fit to booby trap mine as well as thousands of other people's PCs with), I didn't want to replace it with something that might likely do the same as the Bestec did..But I didn't wanna pay $150 for one either, ya know? So the one I bought was somewhere around the $45-$50 range.....Oh and btw the way, the same buddy who loaned me one of his PSUs, has a power supply tester, so after this latest snafu w/ my pc, he brought it over and the new psu tested OK.....

 

[Tedster]

once e-crap PSUs blow, they usually take out the mobo. The first time you tested it, you may have been able to get in it, but it was unstable.

You will need to replace the mobo.

 

[KarmicApexIntel]

once e-crap PSUs blow, they usually take out the mobo. The first time you tested it, you may have been able to get in it, but it was unstable.

You will need to replace the mobo.

Yeah, but this is happening on the 2nd mobo that my buddy gave me, not that first one----that one's blown for sure.
This 2nd one was not one which had been taken out by one o' them thar crappy Bestec PSUs at all--in fact, the system he'd had it in used a diff. brand 300W PSU altogether, he just stopped using it 'cause he wanted to get a more recent-technology mobo....it worked just fine, and I put it through at least 3 or 4 startups using the borrowed PSU, and it never once showed any instability at all; even the boot-up time wasn't slower in any way...

 

[mailpup]

Try borrowing your friend's PSU again. If everything works again, perhaps it is the PSU still. If not, maybe it's the mobo as Tedster suggests but perhaps for different reasons. Something is wrong after all.