I think this is the right place to put this, but to be honest, I don't know if this is a hardware issue or a software one.
The short version is that when I try to play games that require a decent amount of resources to run, about every minute or so (sometimes longer), the game will just...hang there. How long it hangs there depends on how high the settings are, from less than half a second with lower settings, to 2+ seconds with higher/max settings. After hanging there for a bit, it speeds up again before settling back to 60fps (background music is unaffected).
As for diagnosing it, back in February Dell SupportAssist detected that my hard drive was going bad, so they sent me a replacement. With some help, I cloned my old hard drive onto the new one and installed it (I don't have all the details of how this process went since I wasn't the one doing the installation, but I can get those details if needed). Everything seemed fine afterwards, until about a month later (March 24th is the earliest I remember noticing a problem). I tried playing a game on it and was getting the random freezing as mentioned above. I looked around trying to find a solution, trying various things.
I ran CCleaner to clean up the PC as much as possible and fix registry errors. No change.
I did a full system scan (Avast Anti-virus followed by Malware-bytes) to see if a virus was the cause. It did find a few things, which I dealt with. Scanned again afterwards to make sure nothing was left. No change to performance.
I tried disabling Dell Data Vault, as that seemed to be causing issues similar to mine. No change.
I tried closing various programs that I'd have running in the background (Steam, Nvidia GeForce Experience, anti-virus programs [temporarily]) while the game was running. No change. Tried disabling certain background services that weren't necessary (such as Nvidia Stream Service). No change.
I checked the hard-disk for errors. No errors were found.
I checked how fragmented the disk was; only 1% fragmented while it's having issues.
I ran a stress test with Dell SupportAssist. Passed with no problems detected.
I made sure all my drivers were updated. No change.
I adjusted my power settings so that the minimum and maximum processor states were at 100%. No change.
The only clues I have is that LatencyMon detected a possible DPC latency issue (which suggested the processor change I mentioned above as a solution as well as updating the BIOS, the latter of which I haven't tried), and using the "Check for solutions" option in the Action Center gives me the following:
Is there anything else I can try to identify the issue and/or fix it?
My PC:
Alienware X51
Windows 7 Home Premium 64-bit, Service Pack 1
Processor: Intel Core i7-3770 CPU @ 3.40 GHz, 8.0GB RAM
Graphics Card: NVIDIA GeForce GTX 645
If any other info is needed, let me know. I would really appreciate any and all help.