Windows 7: Computer crashes after a few minutes use. Needs reboot

Computer crashes. HP Notebook 64 bit Windows 7 Home Premium, while browsing at times but definitely while looking at video clips, after a few minutes crashes, needing a reboot. Skype dies after a minute or so.
I have checked for viruses
Cleaned the disk
Cleaned Registry
Defragmented
Removed Junk
Windows Repair at the start done
I'm sure the problem is simple but I could not solve it. All suggestions are welcome. Thanks

Cleaned the disk with what program?
Cleaned the registry with what program?

Your specs show your are using two (2) anti virus programs. Avast and McAfee
That is definitely a NO NO.
I would recommend removing McAfee using their own online removal tool.

Find one that meets your needs.
Their are many sites here is one.

McAfee Removal Tool - McAfee Uninstaller

Thanks for the quick response.
Earlier I have had two anti virus programs without them causing any conflict thus concluded that that can't be the reason for it.
I surely would try to remove McAfee as you suggested expecting the right result. Shall return.

Keep this in mind also. McAfee might of damaged Avast. After removing McAfee I would remove Avast and then install Avast again with a fresh copy and update it.
This might not fix all your problems but is the first step.

Could you answer my first two questions in post #2?

McAfee removed as you said.
Avast reinstalled.

Answers to previously unanswered questions, post #2:
Wise Disk Cleaner
Wise Registry Cleaner
Sorry for having overlooked.

So the first step is taken, now I have to keep my fingers crossed till it crashes or never does. Is there any
improvement that can be done now.

First, get rid of the Wise registry cleaner! No telling what havoc its caused your system. If you absolutely feel that you MUST use a "registry cleaner", and they are all snake oil imho, use Ccleaners and LOOK at what you're "cleaning"/deleteing. We see more problems related to this...... practice...... than I care to even think about. AFTER you've done that try running a sfc/scannow to see if you can repair the damage done to your system. Heres a tutorial on how to do that, just click on the blue link : SFC /SCANNOW Command - System File Checker

Actually, I'd get rid of the Disk cleaner too. Anything it does , you can do with a couple of mouse clicks, but thats me. Its imperative you get rid of the registry "cleaner" though.

That is exactly why I asked the questions.

As indianacarnie has suggested I recommend getting rid of both programs.

These work well and are built into Windows 7.

Disk Cleanup - Open and Use

Disk Cleanup : Extended

Ccleaner is a great program but like any thing that fools with the registry you must be careful and know what you are allowing to be changed. It also does a great job cleaning up things.

CCleaner - Download

I would suggest never think that just one problem exist. There can be a combination of things causing several problems.

sfc /scannow is a great little tool built into Windows 7. I use it once a week or so even if I don't have problems. I have never known it to hurt anything.
Windows 7 doesn't like to hurt Windows 7.

As you can see their many tools built into Windows 7. Windows 7 doesn't need all those 3rd party programs like the older operating system did.

If all of the steps suggested as well as these other Troubleshooting Steps for Windows 7
dont help then I would strongly consider doing a Clean Reinstall - Factory OEM Windows 7
to get rid of the HP bloatware which corrupts and throttle's Win7's native performance. We can help you get a perfect install.

I followed your recommendations and ended up with a doing a Clean Reinstall. Everything
was fine and dandy till now, when calamity struck again, even before I could thank you all.

Regarding HP's bloatware, I have no serious grip on that. What are they? Which of these
can be safely deleted?

If you did a Clean Reinstall and followed the steps carefully then you should not have any HP bloatware, just the Win7 OS and whatever programs you reinstall.

What calamity are you referring to?

Did you follow the steps exactly to do the reinstall?

If so then your problem may be hardware-related, so test your hardware from Troubleshooting Steps for Windows 7.

If your PC is still crashing then post up the crash info in our Crashes forum: Blue Screen of Death (BSOD) Posting Instructions - Windows 7 Forums