Need your expertise,

My living room and my bed room are on the same circuit breaker and they are under 15A load.

Lately, I have more devices that connect to the receptacles in the living room, such as:
Denon AVR-4308
XBox360
48 LCD TV
Wii
500W HTPC
And some other devices.

If I turn them all on, likely the power will be out and trip the breaker.
I know that these devices all together may draw more power than the circuit could supply which causes overloading.

Question, can I upgrade from 15A breaker to 20A without running new wires?
It is very tough to re-wire the living room because it is finished and I don't want to break the walls. Any suggestion? I prefer using the same circuit with more amperes.

Thanks in advance.

Nope, 20 Amp circuits require 12 AWG wire.

Why not do the bedroom. Is that enough.

Running circuits, does not necessarily require busting the walls.

Depending on your house and the accessability from above or below (attic/basement) this can be done with the right equipment.

Wire paths can be traced with a high powered toner by circuit.

Once you know the wire path and have reasonable access, you could get buy by adding one outlet hole and outlet and split the circuit at that point.

There a drill bits that are flexible and will drill into the footer above or below. They can also drill sideways. They can be like 48 to about 60" or so.

A video inspection camera also makes things easier.

Good suggestion.

Question: Don't I have to run new conduit? If so, I guess I have to break the walls.

Can I use the network toner generator to trace the circuit? I traced the network cable but not the power wire.

Romex or NM-B cable doesn't require conduit. This is what is normally used in houses.

If you have to run in conduit, there is flex conduit available.

These are the flex bits. greenlee flex drill bits - Google Product Search They require a steering wheel, so to speak to use. Home Depot sells a similar product.

Warning, the power of your drill matters when drilling large holes.

I use a metal low-voltage ring when I drill holes to avoid messing up the walls. You cut the hole in the drywall and insert the metal ring, then drill. The ring I use mounts by just spreading the internal ears.

Yes, you can use a network toner. I'm just not sure of it's range.

If it's in metal conduit or armoured cable, then it won't work.

Before you go wild trying to re-wire the room, what type of wiring method do you have?

If you have conduit, rewiring will be very easy, simply pull out the #14 and replace with #12 wire.

If you do have conduit, I suspect your local code requires all wiring to be done with conduit. But again, if there is conduit exisitng, simple to upgrade or increase the size circuit.