OK, pretty specific set of issues here; I haven't found anybody on forums and the like that seems to have the same.
I'm not much of a computer guy, so any assistance or pointers at all would be truly appreciated.
I'll describe the issue as completely as I can, in this order: 1.system specs, 2.user specs, 3.symptoms and non-symptoms, 4.what I've tried, 5.possible diagnoses(?) and thoughts.
1. System specs
-HP Pavilion g series laptop, purchased in 2011.
-Windows 7 Home Premium, 64bit, version 6.1.7601 SP1 Build 7601
-AMD Phenom II P960 Quad-Core Processor, 1800 Mhz, 4 Core(s), 4 Logical Processor(s)
-Norton and Malwarebytes for anti-bad stuff
-Not sure what other specs would be useful. (Let me know if I should add something.)
-Note: I've never done a wipe or system reinstall, because I've never had a reason to -- everything has worked pretty fine so far, given a troubleshooting session here and there.
2. User specs
-Super vanilla case -- not a gamer, no special software, try to minimize what I'm running at any given time. I don't have lots of programs running in the background (that I know of) and when I run my web browser, I rarely have more than a few tabs open.
-really like Win7 and would like to keep it for as long as I can.
-Not wealthy (to put it lightly) and have had a couple bad experiences with repair people in the past, so I'm a bit non-trusting and would rather do as much as I can (with the help of kind-hearted folks like yourself) before I resort to a tech repair person.
3. Symptoms and Non-symptoms
-Original symptom: random freezing. Doesn't respond to Ctrl+Alt+Del. Mouse cursor still visible. *Occasionally* gives me the Black Screen (maybe 10% of the time it freezes) but stays running/doesn't shut down.
--Doesn't appear to be related to what programs I am or am not running: it happens in the middle of a video, when idle, or after "sleeping". Once while loading Windows.
--Doesn't appear to be related to how long I've been logged on -- sometimes it doesn't freeze for 1hr, sometimes 5 mins.
--It *does* appear to increase in frequency if I log on shortly after rebooting -- it will freeze slightly more quickly than the previous time.
--> NOTE: this symptom is absent in Safe Mode, but apparently NOT in Safe Mode With Networking.
--> Also NOTE: this symptom started soon after a recent series of Windows Updates. Possibly a coincidence, but I dunno.
-Added symptom (a day or so later): parts of the display that should appear WHITE appear BLUE. (well, white with lots of very skinny vertical blue lines).
--this symptom now happens all the time, including in Safe Mode, while doing a "Clean Boot", and while loading Windows (you can see the blue lines in the flashing Win logo).
-Added symptom: the "cmd.exe" window sometimes briefly pops up when Windows is starting. Don't know if it matters, but this didn't use to happen.
-Non-symptoms: for all of the above:
-fan is running normally (i.e. not loud)
-temperature is normal (i.e. not hot)
-lights and screen illumination are normal (even with the Black Screen).
4. What I've tried (with no results)
-Clean out as much dust as I can from the laptop.
-Did a "Forced Reset"
-Ran a malware check.
-Checked all my hardware and drivers on Control Panel-->Device Manager.
-Made sure all my Windows updates, browser plugins, and software I use were up to date.
-*Uninstalled a bunch of Windows Updates, (as mentioned, this problem started immediately after a series of updates.)
-Did a system restore [but I didn't have a restore point before the aforementioned Windows Updates; also I don't have an image to do an advanced system recovery with.]
-Installed BIOS updates.
-Reverted to BIOS setup defaults.
-Ran every HP and Windows diagnostic tool on my computer (hard disk test, RAM test, etc.)
-Uninstalled and Reinstalled the graphics chip driver.
-Consulted HP Support Assistant, Windows Troubleshooting, etc... as well as every online forum I could find a similar problem for.
5. Possible diagnoses(?), Thoughts, Questions.
-My instinct says "graphics chip is screwed", however:
--no problems are listed with the hardware or driver on Device Manager.
--my computer doesn't overheat. (It used to back in the day, but not since I've regularly blown compressed air into it. As mentioned the fan is working normally)
--I don't do anything more visually/graphically taxing than watch Youtube videos,
--For the first week or so, other than the blue lines and the freezing, there was nothing unusual visually: no distortions, artifacts or weird patterns. Photos and video generally load and play normally (except for blue lines in the white parts).
(As of today, I've started to get a couple random red lines here and there. Not sure if they will persist.)
--For the first week, it wasn't running abnormally slowly. (As of today, it seems to be struggling a bit more.)
-I also considered it might be some hardware component reacting allergically to something in one of the recent Windows Updates, but I've uninstalled all the ones that it could have been (*except the security-related ones).
-Why do the blue lines happen in Safe Mode, but not the freezing? (Except it does freeze in Safe Mode with Networking --> is this relevant?)
-Is it worth doing a complete system overhaul and reinstall Windows from scratch, or would that be a waste of time?
-What haven't I thought of?