So, I recently moved into a new home with my family. My room is up on the third floor in the attic, so I need to keep an air conditioner running day and night to keep it cool. However, there's no outlet on this side of the attic so I have a very long extension cable running from one end of the attic to the other. In addition to the air conditior, I have my PC hooked up, an external hard drive(Has its own power.), monitor, and alarm clock. All going off the same exttension cable, most of which are plugged into a surge protector.

Occasionally, something will make a thudding sound and my lights will flicker briefly. I can never tell if that noise is coming from the air conditioner or from the wall. It sounds like the wall. Some nights it happens frequently, like every couple of minutes, other nights it only happens a few times, and sometimes it doesn't happen at all like tonight so far.

I have a TV and game systems that I want to hook up and turn on, but I'm afraid that turning all that on will blow a fuse or something because someone said that the outlet I'm using might be at its limit, especially since I'm using a really long extension cable. Right now I'm compromising by switching the AC off when I wanna use the TV, just to be safe until we can get another outlet or two installed, but that could be weeks from now.

I'm hoping I'm wrong and switching on the power strip that the TV and game systems are plugged into while the AC is running won't blow anything, but I want some opinions before I do anything.

Extension cable could be too long, creates a bit of resistance. You can try using a hub at the outlet, plugging the tv/games in closer, and only have the ac unit on an extension.

I'd say check you cable connections to the sockets... There can be a "cracking" noise because you haven't plugged something in properly, like you computer or your TV. Check your sockets and the cable!

Yep, you're probably overtaxing that outlet. What you're doing is referred to as daisy-chaining, and is NOT recommended. It can be a safety hazard, so I'm glad you didn't try and run everything at the same time.

Just so you understand what's going on, if you live in the USA (which is a pretty big assumption considering the website, but it's one I'm willing to make considering the advice doesn't really change if the assumption is incorrect), that wall outlet has a nominal output voltage of 110-120 volts, and has a max current output of 15 amps. Air conditioners are notoriously power hungry, so it's usually good to give them their own wall outlet. If you're using a small window AC unit, it probably draws about 7 amps on its own. That's almost half your max current draw. As FindMuck mentioned, your extension cord and surge protector are adding some amperage to your current draw, especially if your extension cord is something like a 100 ft and its gauge is anywhere in the teens. So you're probably bumping that up to at least 8 amps with the extension cord in mind.
Figuring out how many amps your other appliances is a little trickier. The alarm clock is probably in the range of milli-amps, so that doesn't matter. PC's and monitors vary so widely by age, model, and usage that estimating the current draw is difficult, but looking at the power supply usually tells you the max power, and if you divide 110 (a rough guess at your voltage) out of however many watts of max power its listed for, that tells you its max current draw. Divide your max current draw by 2, and you have an extremely rough guesstimate of what its drawing. If that, plus the 8 amps we already guessed at is in the 10 amps range, you're right at the edge and risking a blown fuse. If you're at 12, yikes. watch out. If you're higher than that, unplug some things.


tl;dr
Don't daisy-chain. Also, if you're having to reset your surge protector every so often, that tells you you're asking too much of your outlet, and risking a fire. Wait for more outlets.

Valdr that was truly beautiful. The world needs more people like you.