Compaq Presario SR5000 freezes and BSOD

I have a Compaq Presario desktop (SR5000) running Vista home premium
that has, over the last three weeks, developed a nasty habit of throwing
bluescreens and freezups at me. There doesn't appear to be any rhyme or
reason behind them and the mix of stop codes makes no sense at all.
They are (over the last two days) 1A, 7F, 50, 8E, D1, 0A, D1. Various
"reasons" are:

"PAGE_FAULT_IN_NONPAGED_AREA"
"DRIVER_IRQL_NOT_LESS_OR_EQUAL".

Two days ago, in vain hopes to upgrade my MOBO video (Nvidia 6150) with
a Zotac GeForce 8400GS (1G of RAM), I purched both the video card and a
new PSU. The original PSU was only 250w and that was nowhere near
enough for the new video card. The new PSU is 450w.

I ran Aida64 Pro on this machine and saw that the 3.3v rail was showing
only 1.744v. Very low. I checked with my DVM and found it to be
sitting at 3.312v; so Aida is reporting it wrong. However, I am
wondering if perhaps something on the MOBO-side of the sensor is what is
causing Aida to read improperly. No strange smells that I can detect.

I have 2 RAM sticks: 1G and 2G, I've swapped places with each other,
tested them singly and together using MEMTest all night. No errors.

I've run HDTune many times and no HDD faults have shown up.

Using Aida, I've run stress tests on system memory, CPU, and HD - no bad
results.

There doesn't appear to be any set pattern to the screen freezez. I can
be working along and BAM, the screen freezes and no mouse or KB input is
accepted. I have to power down to recover. The Event viewer is of
little help in that it only dutifully reports "the previous shutdown at
xx:xx:xx was unexpected" well, gee - ya think?

A couple of the files pointed to by the blue screens are: SSORP RT.SYS,
NTFS.SYS but they aren't the only ones. In some cases, I can get the
computer to fail by running my Avast! antivirus scanner on the HDD.
Pretty much every time I get down into the system32 files, I will either
get a screen freeze or a bluescreen. The same is true of a MalwareBytes
scan. I am pretty sure I don't have a virus, but one never knows.

Bluescreens and freezes will happen in either Safe Mode or normal mode.
I've tried a clean boot and let the OS "find" every device I have.
This does not help my problem.

I've been in the business of IT and computer operation/repair for almost
50 years now and I'm really stumped on this one.

Sorry for the long post.

--->
> I have a Compaq Presario desktop (SR5000) running Vista home premium
> that has, over the last three weeks, developed a nasty habit of
> throwing bluescreens and freezups at me. There doesn't appear to be
> any rhyme or reason behind them and the mix of stop codes makes no
> sense at all. They are (over the last two days) 1A, 7F, 50, 8E, D1,
> 0A, D1. Various "reasons" are:
>
> "PAGE_FAULT_IN_NONPAGED_AREA" "DRIVER_IRQL_NOT_LESS_OR_EQUAL".
>
> Two days ago, in vain hopes to upgrade my MOBO video (Nvidia 6150)
> with a Zotac GeForce 8400GS (1G of RAM), I purched both the video
> card and a new PSU. The original PSU was only 250w and that was
> nowhere near enough for the new video card. The new PSU is 450w.
>
> I ran Aida64 Pro on this machine and saw that the 3.3v rail was
> showing only 1.744v. Very low. I checked with my DVM and found it to
> be sitting at 3.312v; so Aida is reporting it wrong. However, I am
> wondering if perhaps something on the MOBO-side of the sensor is what
> is causing Aida to read improperly. No strange smells that I can
> detect.
>
> I have 2 RAM sticks: 1G and 2G, I've swapped places with each other,
> tested them singly and together using MEMTest all night. No errors.
>
> I've run HDTune many times and no HDD faults have shown up.
>
> Using Aida, I've run stress tests on system memory, CPU, and HD - no
> bad results.
>
> There doesn't appear to be any set pattern to the screen freezez. I
> can be working along and BAM, the screen freezes and no mouse or KB
> input is accepted. I have to power down to recover. The Event viewer
> is of little help in that it only dutifully reports "the previous
> shutdown at xx:xx:xx was unexpected" well, gee - ya think?
>
> A couple of the files pointed to by the blue screens are: SSORP
> RT.SYS, NTFS.SYS but they aren't the only ones. In some cases, I can
> get the computer to fail by running my Avast! antivirus scanner on
> the HDD. Pretty much every time I get down into the system32 files, I
> will either get a screen freeze or a bluescreen. The same is true of
> a MalwareBytes scan. I am pretty sure I don't have a virus, but one
> never knows.
>
> Bluescreens and freezes will happen in either Safe Mode or normal
> mode. I've tried a clean boot and let the OS "find" every device I
> have. This does not help my problem.
>
> I've been in the business of IT and computer operation/repair for
> almost 50 years now and I'm really stumped on this one.
>
> Sorry for the long post.

Rats. I also meant to add that I've run the command SFC /SCANNOW
several times (both in Safe mode and normal). It reports that some
files could not be "fixed". CHKDSK (run at boot time) checked the
entire drive fully for bad sectors and reported none.