Pavillion m9077c lockup and fuzzy screen

Question

My computer locks up with a fuzzy screen
I have an HP Pavilion m9077c-b quad core computer running Windows 8.1.  It has an Nvidia GeForce8500GT video card and I suspect it is going bad, but haven’t convinced myself that it is the problem.
I checked the following:
Overheating (Checked with SpeedFan Program)
GPU temperature initially 79° C
After blowing out the case, temperatures ran in the 72-75°C range – still lock ups
With fan blowing into the case and the temperature at ~67°C, still locked up.
All 3 fans, PS, GPU and case fans are running
Note – GPU Temperature may be slightly high, but seem to be within specs for Nvidia
Drivers
Updated Nvidia driver
Installed a Nvidia hotfix dated 4/15/14 – Still locked up
Other pertinent drivers seem to be up to date
In NORMALmode, had lockups running the following, mostly individually, but sometimes in combo:
File Exp
MS Outlook
lorer & Adobe PDF
MS Digital Image
Internet Explorer
Web Camera
MS Word
Turbocad (3D rendering program like Autocad)
In SAFE MODE, ran most of the above overnight with no problems (but no video card?)
In SAFE MODE WITH NETWORKING, ran most of these programs for 8 hours with no lockupsl
Video Card
Using HP’s Support Assistant program Video Check
       i.      Lock ups in SELECTIVE START UP – runs to 56% & 90% then locks up
      ii.      Lock ups in SELECTIVE START UP with networking
     iii.      Runs in SAFE BOOT WITH NETWORKING -- no problems (but doesn’t check the GPU?)
Ran dxdiag in SELECTIVE START UP with no problems detected
Motherboard & CPU – tested with HotCPUTester4Pro
In SELECTIVE START UP – ran diagnostic test for 5 hours with no problems
In SAFE BOOT WITH NETWORKING -- ran diagnostic test for 5 hours with no problems
Disk Drive – ran Scandisk with no problems detected
Power Supply -  changed out ~2 years ago with a premium power supply.  600W Thermaltake.
Any thoughts on what might be causing the problems, and if it is the video card, is there a better way to confirm it is the source?

Answer 1

Yes, it definitely could be significant.  Do you have a friend who could loan you a video card to see if it works?  This would be helpful.
Signature:
HP TouchPad - 1.2 GHz; 1 GB memory; 32 GB storage; WebOS/CyanogenMod 11(Kit Kat)
HP 10 Plus; Android-Kit Kat; 1.0 GHz Allwinner A31 ARM Cortex A7 Quad Core Processor ; 2GB RAM Memory Long: 2 GB DDR3L SDRAM (1600MHz); 16GB disable eMMC 16GB v4.51
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HP Photosmart 7520 AIO
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