Is it possible to take a desktop PC as carry-on luggage?

If you do take it and store it in the hold, I'd suggest removing the harddrive. You don't want that bashed around by other suitcases.

Taking it as carry-on - as long as it fits in their luggage dimensions (the airline you're using will have this on their website) and is under their weight restrictions (you sure it weighs less than 8kg?), then there's no reason you shouldn't be able to. People take laptops all the time, and yours is just a bigger, bulkier version ;)

However, what I'd pay to see is the looks on peoples' faces at the xray screening checkpoint, where they tell you to remove the laptops from your bag. Naturally, I'd expect you'd probably have to take your desktop out of the bag as well, and it'd be fantastic to watch :)

A quick searched showed me that another guy has done this before, with similar reactions, and from the sounds of it he had no problems at all.

When I went from US to India, I decided to carry my desktop with me, minus the monitor. The main reason being I didn't find the corresponding motherboard specs in India (although it would be available in a few months!). As I knew how to put together a computer and also knew that I could buy a new case in India, I dismantled the entire computer and took only the components. I decided to carry the hard drive in my carry-on baggage but decided to check in the motherboard and power supply. Everything got wrapped in layers of clothing so that they wouldn't be damaged.

At the US end, there weren't too many questions. When I landed in India, when the luggage got x-rayed, there were questions about an object with lots of wires coming out of it, but when I explained, there was no problem.

Once I put it together, the computer ran without a hitch!

I just took my dismantled desktop through security with me at Singapore Airport, no question asked.

I did exactly that when I moved from Argentina to Canada in 2002. Via the US, so there was Argentinian security at EZE, American security at EZE, again American security in the US, and then Canadian security.

The most annoying ones about it were the Canadians, both at check-in with Air Canada and at security. At check-in, the employee wouldn't believe that it was within the carry-on limits. I had done my homework, so the case fitted (barely) in the measuring basket and they had to let me go through. Security was different; they wanted to apply the same policy than they had for laptops, which was that you had to turned them on. I told them I was completely ok with turning it on, as long as they provided me a monitor and a keyboard; that could have gone bad, but somehow it worked (though I don't recommend it).

I advise that you disassemble the PC, securely wrap the components individually, and leave the case at home. Cases are relatively inexpensive and you can buy a new one at your destination. It will be a small part of the overall cost of your move.

The individual parts will take up much less space than the entire case and will be much easier to carry. You also remove the risk of the graphics card (or anything else) snapping off the motherboard in transit and breaking.

Desktop PCs aren't really designed to take bumps of any kind or be anything other than perfectly upright at all times. I wouldn't like my chances of leaving a tower on its side in an overhead compartment during a long flight.