Hi all, hopefully someone here is going to be able to solve this problem for me!

My PC seems to be completely locking up almost every time when being accessed over LAN, and less frequently when reading/writing to external drives.

I can't think of anything particular that has changed and started the problem, but I have installed multiple games, apps and updates between it never happening, and it being constant, so it'd be a lot of work trying to isolate anything without any direction. Of course it's one of those things you don't do everyday so it's impossible to pinpoint the exact time it started happening.

I've run Avast and CCleaner as typical maintenance tasks, ran Chkdsk, and checked the Event viewer, all of which were inconclusive.

Event viewer shows completely normal activity up until the file transfer starts, which is when the system crashes, which has absolutely no documentation, indicating to me that the computer is totally jamming up, meaning not even the Event Log can capture information.

Specs:
Win 7 x64
AMD Athlon 64 6000+ x2
5Gb DDR2
500Gb SATA HDD
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What kind of NIC do you use? Onboard or a PCI/Mini PCI-E model?

PCI Wireless card. I don't get any problems from connecting to the internet/playing LAN games so I don't suspect the card to be the source of the problems.

So you can play games via internet without any problems. Hmmm...

I reread your description once more and conclude that your PC either freezes when another computer tries to access it via your WLAN or less often when you write/read from external harddrives. By external harddrives you probably mean harddrives, which are connected via USB? Is that correct?

The crash in itself, how does it look like?

a) system freezes, same image stays until you reboot the computer by force (reset button) and nothing shows in the event viewer
b) screen turns black, system reboots
c) system simply reboots

Tricky to say what this precisely is, but somehow it reminds me of an enigma which I encountered in 2004 while doing tech support. The system behaved as strange as yours and a reinstallation of the system didn't help. I also haven't heard of this particular hardware fault for a long time, but it will very likely just take you a few minutes to open the machine and take a look at the capacitators of the mainboard to make sure they don't appear bulged or even leaking.

Yes, actually not just external, moving/copying files from my other internal drive can also trigger the crash. I have tried taking out the other drive to see if it was the culprit, but it still happens.

Here is a list of causes in order of how consistently they crash the system

1) (Every time) Transferring files over WLAN
2) (Almost every time) Read/Write to other internal drive
3) (Now and then) Downloading Torrents (The latest Project CARS installer got it), and Read/Write from USB stick.

Downloading files from regular HTTP servers does not cause the issue at all.

The crash is a complete freeze. At for the first couple of seconds the cursor begins to stutter, 2 or 3 jumps, then sticks in place, any flashing bars go solid and well, it's like looking at a screenshot. Sometimes after about 15 seconds, the mouse will jump to another place on the screen, once. After thats happened, it's totally halted. At this point I hard reset. I'll take a look at the caps.

Thanks for the description.

Gut feeling - I stick to checking the caps. If that doesn't bring a result, I'd de- and reinstall the chipset driver(s). I know, you use a PCI-WLAN card, but in the end it's stuck in the mainboard as well.

So reading and writing files from/to other internal drives cause this freeze as well, so that's just more reason to assume a flaw with the mainboard. Btw, which mainboard model is it anyway?

You could download Coretemp and turn on logging so you can see what it is spiking your memory right before the lockup.