I think the thread title gives sufficient impetus, but last night I noticed a slight burning smell while gaming.
I have been admittedly lax in dusting this computer (not TERRIBLE inside, owing to good filters, but the filters were in bad shape and it was due for a good cleaning).
I think, judging by where the smell seems to be coming from, that it's out of the graphics card (and it's not like I can see inside the thing with its fan and case and all). I'm reasonably sure it's not the PSU, on account of its fan not even running (not under enough load I guess? I may have ended up with overkill there, I'm not sure and I put this together like 3 years ago).
I'm not really sure how to diagnose what's wrong any further, but I would REALLY like to not replace a graphics card if I can help it.