Originally Posted by Melkane
Actually if you replace it you should be able to switch Harddrives out.
Though with 3 red lights you should just call Microsoft, they are giving free repairs on all 360s with 3 red lights and they are extending warranties on that issue for 3 years.
Instead of buying another 360 that could suffer the same problem (Microsoft has admitted all 360s made up till now have the problem that can cause the red lights, you can get your current one fixed and have it better than buying another one or having it replaced.
If for some reason Microsoft gives you a hassle about it there is a guide online on how to fix the 3 red light problem yourself. Though if you do you void any warranties.