Power Cable? Just about any hardware/general store sells extension cords, you shouldn't have trouble with that one. lol
HDMI cables come in lengths up to 100ft at newegg.com, I'm sure 50ft+ can be found at a large number of electronic stores.
Mouse/Keyboard, once again all you need to do is buy USB extension cables, not sure how long they come. Maybe a wireless set up would work too.
Personally I think it would be cheaper/easier to replace the noisy fans in the computer so it's no longer noisy.