Hp touchsmart300 pc shuts down, the screen is black, power button is lighted but not responding?

Question

HP Touchsmart300 PC with operating system Windows 7.
The PC shuts down even when active. The power shuts down although the power button is still lighted. It does not respond to touch, keyboard, or mouse. The only way to get it back on is by unplugging the power and then restarting windows. I already checked Sleeping Mode and Power Options in control panel, but no problem there.

Answer 1

I can totally empathize with your situation, as I too had the same exact issue with my HP TouchSmart 300. In fact, I have been dealing with this problem off and on for the last year. I have worked with HP tech support on numerous occassions. I have had them remotely control my computer and restore it to factory settings. I have reformatted my hard drive 2 or 3 times. I have tried multiple anti-virus software programs, removed anything that might cause a conflict with the operating system, etc. Basically, nothing was working for an extended period of time. And, of course HP tech support as this point to me, was essentially useless in resolving the problem.
It seemed like every few weeks it would start shutting down again. I started researching potential causes and discovered that I was not alone, in terms of the same issue with this computer. From what I read, in many forums like this, it seemed like the probable cause had to do with either the power supply, or overheating. I felt like the problem might be due to the system overheating, so I removed one of the back covers, which worked for a short while. I then removed a second cover, which helped for a few days. I even placed a 20 inch box fan behind the unit to try and cool it down (which still remains in place). However, my computer would just keep shutting down over and over again. 
Finally, as I was long ago out-of-warranty, I just decided to completely open-up the back of the unit and poke around a bit. I cleaned out all of the system fans, reseated my memory cards, and ran the computer for a few days with all of the covers removed from the back. It would still keep shutting down. However, I did notice that the heat sink and attached copper tubing were pretty hot (even with the 20 inch fan blowing directly on them). So, I removed the heat sink apparatus from atop the CPU. I discovered that the thermal gel was pretty much long gone, and what was left of it was not so evenly applied. So, I ran over to the nearest computer store, and purchased a tube of thermal gel (for about eight bucks). I found some rubbing alcohol and cotton swabs in the house, and proceeded to use those to carefully remove the old dried-up thermal gel from the top of the CPU chip, as well as the heat sink plate (if that is the right word for the part). I applied a fresh even layer of thermal gel to the top of the cpu and placed the heat sink back on top. I turned the system on, and it has been running smoothly ever since (about 2 weeks without a single shut-down). I have even noticed an increase in performance. The top of the heat sink is noticeably cooler to the touch now.
I realize that your situation may be different, but if your system is out-of-warranty, you might consider this option. It seems to have resolved my problem. I will repost an ocassional update if anyone is interested, thanks.