BSOD and Computer Lockups - Failing Components?

Hi, my PC has been acting very obnoxiously as of late. Occasionally (2 - 3 times a week), my PC will just crash and go to a BSOD - I'm sorry, it hasn't done it in a week surprisingly, I will wait for the next one to give you the code. Upon restarting, sometimes it will boot from my secondary HDD and I will have to change the boot order in my BIOS. It will also hang at the Windows splash screen for about 10 minutes before fully starting up. Other times, my PC boots up just fine which leads me to believe its a failing component (hopefully just a HDD issue?).

Another issue, which is more consistent than the others, is that my PC will just randomly hang for 3 - 15 seconds before resuming. It happens while gaming primarily(or maybe I just notice it more while gaming), although other programs lock up as well.

I ran a memtest and found no errors, I ran checkdisk and it found no errors, I'm not sure what the next step should be.


Brief recap of symptoms/TL:DR:

-Occassional/Frequent BSOD (have to write down code next time)
-HDD Boot order randomly changing during reboot (HDD detection issue?)
-Occasional/Frequent long boot time (windows 7 splash screen for 10 minutes)
-Frequent 'hangs' (3 - 15 seconds of complete lockup, then back to normal. Windows doesn't completely lockup, but programs do.)
-Program inconsistency/crashes. Skype locks up for a moment, then continues. Occasional program crashes, etc. Music will randomly stop playing for a moment, then continue.

Thank you for your help!

"Upon restarting, sometimes it will boot from my secondary HDD"

In my experience this means you have an intermittently failing hard drive, which means windows will intermittently fail as well, and also means you probably have some corrupted files now within windows, and since its intermittent it may be difficult to pinpoint. I recommend you download then boot from the (free) Ultimate Boot CD, doing so initially with your primary hard drive unplugged from your motherboard. Run a few of the tests, like cpu and memory. Assuming you pass these tests without errors, its likely that your hard drive is the problem so plug it back in, boot UBD once again, then perform some hard drive testing. The reason I suggest this path is because windows itself is probably corrupted if the hard drive is bad, so its best to do some initial testing with both windows, and your hard drive, removed from the equation, hence the strategy of booting from a bootable CD environment.

Another thing that can cause intermittently re-ordered boot drives is a corrupt bios. When you boot your machine your bios "mates" your hardware to windows so if your bios is corrupt at all this process does not work and windows won't know how to address your hardware, giving you weird errors such as an unrecognizable hard drive. So updating your bios may help. Even if you are on the current version of bios, if its corrupted you should refresh it. But based on what you wrote so far, my money is on a bad hard drive.

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Okay, I'm back with an update:

Yesterday, my PC did it's usual hangup, but never recovered and went into a BSOD. I tried writing down the code, but couldn't get the whole thing as I wasn't quick enough. It was 000000F4 or something similar. Either way, I could never get the machine running properly again. Every time I restarted, the computer would soon completely lock up.

Eventually, I installed Windows on a secondary HDD and am now using that. I guess if the problem doesn't return, it was an HDD issue and we have our answer. If it comes back, I will follow all the steps you guys outlined above.