If I shut my PC off, the next time I try to boot up, it freezes on the HP blue screen (does not make it to Windows XP screen). This has been going on for a couple months now.

If I shut my computer off, unplug it from the wall for 10-15 seconds, plug it back in, it boots up fine.

So, I either have to never shutoff my computer, or unplug it before I start back up so it boots up.

Replaced the power supply, still had the same problem. Put old power supply back in.

Unplugged the hard drive and booted, still had the same problem (don't think its making it to the HD in boot).

Unplugged the DVD rom and CD-RW drives to eliminate them, still had the same problem.

Now, I have a new, related problem, happened first time 4 days ago, now happen a few times a day. The computer shuts down, not a normal shut down, just instantly to blank screen no power on PC. Again, if I unplug for 10-15 seconds, it will boot back up (though sometimes I have to try the unplug trick 2-3 times to work).

Any ideas on what this could be?

Could a bad motherboard cause this? Heat sink?? (note I am an experienced beginner in computer skills).

My fan is running. Actually, it runs all the time. Hardly ever shuts off.

Computer is in a hutch. Door is closed but cut hole in back the size of the tower so fan blow out the back and there is 2' of space between the hutch and the corner walls.

What about something as simple as the CMOS battery

Judging by what you are saying with the Blue Screen it sounds as though it is your BIOS.

You need to update your BIOS. Contact HP directly and they will talk you through how to update the BIOS for your particular machine as there are many updates available for different machines.

This seems like its more of a power issue to do with the Soft power settings in your BIOS rather then your Motherboard or power supply.

By all means you could also try changing the CMOS battery as the settings will be lost if the battery is dead. give it a go

Here are my computer specs:

HP Pavillion 061 PS567AA-ABA a1100n
Running Windows XP Home (SP2)
2.93 Ghz Intel Celeron
HD: Intel 82801DB Ultra ATA 80 Gb (52Mb free)
MB: ASUSTek Computer Inc Guppy 1.03
133 MHz Bus
Phoenix Technologies 3.04 BIOS
512 MB RAM (Slot A0), Slot A1 empty
DVD Rom drive
CD-RW drive
Onboard sound
Onboard video
PNR Planar PE1901 (19" LCD) monitor
HP 6122 Printer
HP 3970 Scanner
Logitech STX QuickCam
HP PS2 Keyboard
MS IntelliPoint USB mouse
4-1 card reader
Firewire connection

I updated BIOS from HP site last night, no change.

Used HP software to run CPU test with result that all is OK.

Ran RAM test with windiag with result after 1st pass that all was ok

I think I have a heat problem. I installed SpeedFan and Prime95 last night. Temp1 is 80C at 5%CPU and as high as 105C (Yes C)after 15 minutes taxing 100%CPU.

CPU is in computer hutch with back open to the size of the CPU. Will open up more tonight.

Was told by another to check and make sure the heat sink is fully snapped in.

Caps look OK, no bulges or brown fluid, but the unplugging required for proper reboot makes me suspicious of them.

Computer is a little dirty inside but not horrible.

OK, again my computer was a little dirty but not horrible. Blew it out with air last night, especially the heat sink. This solved my intermittent shut down problem and my startup problem (where I had unplug the computer from the wall for it to boot up). Before cleaning my temp (via Speedfan) was 80C and my fan ran at 4000+RPM at 5% CPU and was 105C and 4000+RPM at 100%CPU (via Prime95). After cleaning my temp (via Speedfan) was 40C and my fan ran at 2200+RPM at 5% CPU and was 50C and 2600+RPM at 100%CPU (via Prime95).

Moral of the story, don't be a slob, clean, clean, CLEAN!

Listen up people... HEAT is a MAJOR contributor to a lot of PC power fluctuation problems.

Think about it... When you're hot you feel like doing nothing. A PC won't do anything