My computer is a dick!
For the last couple of weeks it won't start properly and needs several tries until it's successfully booting. Once it made it this far it happily runs smoothly all day. The starting problems are still hella annoying. >:[
As of now we've replaced almost all components with the ones that were in my bf's computer. The kicker? In his computer case my hardware works just fine while my computer still doesn't start properly - even with his hardware! WHAT THE HELL!?
We're running out of ideas. :cEdit:
We found the problem. It was my monitor! For some shitty reason it caused the fuss when starting the computer. Anyway, thanks for your help!

Now I need to buy a new monitor. Damn, this will cost money.
(Currently writing this from our notebook.) Pants are an illusion... and so is death!
And yes, recycling goes without saying. There are regulations here in Germany that requite you to take your e-waste to a disposal site for, well, e-waste where it will then be recycled.