MSI Z77A-G45 and Samsung 840 Series weirdness

Question

Ok so here's the thing
about a week ago i decided that it was time to build a new computer with a Z77A-G45 motherboard
put it together, installed windows 7 64-bit and everything was working just fine - for about 5 days -
but then one morning when i turned on my computer it decided not to boot and just sat there with fans running with an A2 code at the bottom left of the screen
i tried taking out the ram leaving just 1 in and moving it to different slots and trying a different ram block boots thinking it might be faulty ram,
when that didn't work i tried removing the graphics card and boot with just the onboard VGA, reset the CMOS jumper, and even replaced that battery on the motherboard thinking the shop might have shipped an almost dead one, took everything apart and booted it outside the case on a glass surface to make sure it wasn't some sort of short
but the only time it actually wanted to get past the A2 code was when i booted with only 1 of my hard drives, so  i started changing my drives around using various combinations of SATA cables and ports (luckily had an extra 5 SATA cables lying around)
eventually i narrowed it down to it wanting to boot with 2 of my 3 drives but the 3rd one (a Samsung 840 series 500 GB SSD, that has no system files or anything fancy other then music, movies and a few games at the moment) getting it stuck on the A2 code
so i set it up as an external USB drive with a SATA/USB converter i had sitting around but then it would get stuck on B4 instead if i booted with the drive connected
however everything would work just fine if i connected the drive after the system had booted up (or even just unplugging and replugging it when it got stuck on the B4)
once back in windows with the drive connected i ran all the diagnostics i could think of but nothing showed anything wrong with it
(and the only thing i had done with the drive before it stopped wanting to boot was to defrag it)
eventually i decided to copy all the files from the drive to a different drive and reformat it as sort of a hail-mary
and to my surprise that actually made it boot up just fine
so i moved it back inside the case as a normal drive just to make sure it would still work (which it did) and then moved all the files back to see if any of them were the culprit - that turned out not to be the case however
it booted up without complaint with all the original files on it
so now my question is why?
what the heck is going on?
did defragging cause some sort of data fault that caused the bios to not be able to read the drive properly or did i just buy a haunted computer?
like i said everything is back in the state it was the day before it didn't want to boot and bios and been defaulted so it's not really an issue at the moment but I'd still like to know what's going on so i can hopefully avoid it in the future
any answers or comments will be appreciated
for your reference a full parts list:
Motherboard: MSI Z77A-G45
Bios Version: 2.10
Graphics card: Club3D GeForce GTX 550ti 2GB
PSU: Corsair TX 950W - 100-240V ~ 12A 50/60Hz
CPU: Intel Core i7 3770K / 3.5 GHz Processor (Stock boxed fan)
RAM: Corsair Vengeance - 32 GB (4 x 8 GB) - DIMM 240-pin - DDR3 - 1600 MHz ( PC3-12800 )
HDD: OCZ-Vertex2 128GB SSD (OS)
         Hitachi HDS722020ALA330 2TB HDD (Media/Backup)
         Samsung 840 Series 500GB SSD (Media/Backup)
OS: Windows 7 64bit Ultimate

Answer 1

This is strange
I have Z77A-G43, and have exactly the same problem with one 1GB sata drive, that works just fine in every other PC.
In my case PC run into restart loop, but with same code A2 as yours.
Strangest part was PC was restarting even if I put HDD into PCI Sata/Raid card !?
So I am guessing here its not a hardware problem, but a software (BIOS) problem.
Now whole pc with Z77A-G43 is at Service because of faulty DVI output (not working).
Will try reformating drive, but need first to buy >1gb hdd to backup that one
Drive is currently working just fine in this 10y old MSI PC =.=
It seams they have stopped making things as they used to, this old mb is one durrable dog.
which was the main reason I went to same company when in question was mb...