I have had this computer (stock except for a Win7 64-bit upgrade from Dell after I bought it)  for about three years and it's been a champ but recently the graphics card started to give me bad screen artifacts so I upgraded the card and the PSU.  I chose an XFX HD7770 and a Corsair GS700 and took advantage of the emptied out case to blow out any nagging dust but I had already blown out the case earlier in the month.  The new items installed easily but the computer has bad issues since:

1.  The LED on the motherboard near D27 is no longer green but solid amber

2.  The computer fails to boot into Windows normally.  Instead:

      - Posts (without any beeps) and starts the windows loading screen

      - When the four dots swirl and make the windows logo the USB seems to 'shut off' and the mouse and keyboard lights go out

      - The windows logo pulses as normal for about 5-10 seconds and then BSOD with Machine_Check_Exception error and reboots

3.  BIOS settings check out normally and the Dell BIOS diagnostic stuff finds no faults on the detailed check (Takes hours!)

4.  Windows will boot into SAFE mode w/networking and I can use it for hours without any issues at all

5.  Checking the load error log shows that the last thing that loads before the failures occur is CLASSPNP.SYS (but the SAFE mode boot shows that file being loaded and it does proceed into a normal SAFE mode start)

What I've done so far:

1.  Tried the old PSU and GPU but they behave the same as the new ones

2.  Removed and reseated ALL connectors on the MB (including the front panel USB connectors) (Unsuccessful)

3.  Tried booting without the front panel USB connected (Unsuccessful)

4.  Removed and reseated all RAM (Unsuccessful)

5.  Tried booting with nothing but HDD, CPU, Video and RAM connected (Unsuccessful)

6.  Removed CPU heatsink, cleaned sink and CPU, reapplied thermal paste in case the old paste seal had been disturbed by PSU changeout (Unsuccessful)

7.  Replaced CMOS battery with fresh 2032 (Unsuccessful)

8.  Cursed.  A lot.

So I am unable to figure out what is going on yet but I'm still trying to figure it out.  Does anyone have any suggestions to help me move forward?  I don't have any good way to test the PSU and I suppose it's possible that I have a bad one but it's odd (to me) that I can get into SAFE mode fine but not normal bootup.

I'm leaning towards perhaps a software error but Machine_Check is seems very specific to hardware failures from what I've been reading.  I have tried to repair windows (when the option to repair or start windows normally pops up) but it BSODs the same way.  I guess the next step would be to try the whole system restore but it just doesn't seem like that should have to be done since the PSU isn't driver/resource oriented and video cards are intended to be swapped out without having to reinstall windows.