I'd try another power supply first. Borrow one from another PC if possible.

Looks like a sticking power switch. Power switch is a momentary contact switch and if it stays depressed, PC will shut off after about 3 to 5 seconds.

Disconnect power switch from motherboard and...

Use PSU recommended by 4th&3wood.

Any luck with ATX PSU?

Re PSU form factors:

Realized that HP has used both uATX and SFX PSUs in their PCs. If PSU has 3 mounting screw holes it is SFX and uATX if it has 4 mounting screw holes. uATX is same as ATX...

How about posting the beep code (pattern) along with BIOS installed. Beeps can mean a lot of different things.

You need a rear exhaust fan otherwise the PSU will suck in CPU cooler exhaust. While CPU and ambient temps may be OK, PSU will run hotter affecting its life and stability. You'll probably be OK as...

You very well may have a failed motherboard or CPU rather than power supply. Although a standard ATX power supply will not fit inside your case, the connectors are identical and one can be used for...

Connect a monitor to VGA port on notebook and see if you get a display.

Is there a flashing cursor in upper left hand corner of black screen?

Windows is failing to start because it cannot recognize SATA hard disks -- possibly due to boot sector corruption.

Connect each SATA hard disk singly (no other disks connected and SATA controller...

Is power LED blinking amber? If so, you have either a faulty PSU or motherboard.

If display freezes rather than blank screen or reboot, problem is likely caused by video card. Overheating of video card will produce those symptoms (frozen display).

Try a basic boot. Disconnect all drives (signal and powe cables), remove PCI cards, disconnect all external devices except keyboard and monitor. Use one stick of memory at a time.

Have you...

Can you read controller chip information? Manufacturer and model.

Most inexpensive cards use SiI chips. Generic drivers are available on SiI website and elsewhere.

I've already given you my best advice which you apparently ignored.

Those voltages are fine. You cannot change them (either up or down). You can only change CPU voltage and memory voltage on motherboards that support tweaking and overclocking.

What about CPU...

1. Yes, removing battery clears CMOS. The Clear CMOS jumper does the same thing. CMOS is volatile memory and flushes when power (battery) is removed. CMOS is powered from 3.3VDC when PC is on.

2....

If CMOS reset doesn't work, it wouldn't hurt to try another CMOS battery just in case yours is faulty. They are cheap and easy to replace. Available at Wal-Mart and Radio Shack (CR2032 coin cell).
...

P35 chipset mobos start for a few seconds, turn off for a few seconds and restart on initial boot. BIOS plays a role in this behavior.

Try resetting CMOS. A BIOS update would probably help, but...

Yes it does have to be a 1333MHz or 1600MHz FSB motherboard to support that CPU.

Motherboard I recommended uses DDR2 RAM.

You will need a Socket 775 motherboard that supports 1333MHz FSB CPUs.

I prefer this one (for non RAID):
http://www.newegg.com/Product/Product.aspx?Item=N82E16813128059

Very nice mobo at a...

Hard to say exactly what cause is, but I'd start by replacing CMOS battery. It's cheap and easy to replace. You may be losing CMOS settings.

SMART test failure means HDD is failing. I've never seen SMART return a "false positive" failure message.

Looks like you have it narrowed down to PSU or motherboard. If swapping PSUs doesn't resolve the problem -- well mobo is left.

Inspect capacitors on motherboard for signs of swelling or leakage,...

I agree with New Normal that E6600 is best CPU for your mobo considering currently available CPUs. Second choice is an E6400.

Now how about marking previous question solved?

XP and Vista install differently - Vista uses an image file.

Test memory before going any further. Memtest86+ and other handy utilities are on the UBCD.
http://www.ultimatebootcd.com/download.html

According to eMachines web site, you have an Intel i810 chipset. Install Intel i810 chipset and video drivers from following links first. Install in order listed.
...

Test memory using Memtest86+. DOS only uses the first 1MB of memory and memory above that may be faulty.

If it's a memory issue, Linux will fail as well.

As I said before, motherboard LED lit only means 5VDC standby power is present. It does not indicate that motherboard is functional.

Odds of a single faulty CPU are very small. In 90+ percent of...

No, the motherboard was manufactured by BCM (GVC) and rebadged to a Micronics -- I was wrong about that being video card.

BIOS manufacturer code shows actual manufacturer.

Both manuals are for...

I recommended trying each stick of RAM in first response. Why didn't you try that instead of asking more questions?

I'm all out of ideas at this point. I don't understand why BIOS is seeing keylock enabled with keylock pins unjumpered.

CMOS batteries usually work fine at 3.0V or above. A fresh battery should be...

PSU or motherboard in all liklihood. Take bobbyraw's advice and try another PSU first. Disconnect all drives and remove PCI cards while testing.

Inspect capacitors on motherboard for signs of...

A long shot -- try a USB keyboard if you have one or can borrow one. A USB keyboard may not work on a PC of that vintage, but it's worth a try.

What was voltage on CMOS battery? If less than 3.1V,...

See this link:
http://h10025.www1.hp.com/ewfrf/wc/fastFaqLiteDocument?lc=en&cc=us&product=18703&dlc=en&docname=c00809678

Make your next purchase -- after a PSU -- a battery backup (UPS). Inexpensive way to protect a PC from voltage fluctuations.

No time outs that I'm aware of. Try removing battery again and leave out for at least 5 minutes. Maybe clearing CMOS again will help.

Jumper across keylock pins is only active when PC is powered...

I don't think low amperage 12VDC will give you too much of a curl :)

What have you tried so far?

Unshorted is unlocked and vice versa. Keylock switch is not needed. Remember, I recommended jumpering and then unjumpering pins. Wouldn't hurt to try with PC powered on as well. Just use caution.
...

See my earlier post again -- edited to add last sentence.

BIOS string also tells you that it's an Intel 440LX chipset motherboard.

Yes, keylock pins are for a physical keylock that was used on...