First you state Desktop then Laptop ?
Take the battery out, plug in the charger and see if the laptop works.
If it works, the battery may be the problem.
Check the AC Adapter
Check to make sure the adapter is plugged securely into the wall outlet, connected firmly to the adapter box and to the back of your laptop.
Most AC adapters have a little light in themon that rectangular box in the middle of the cord that lights up when it's getting electricity.
If that light isn't on, try a different outlet.
Check your fuse or circuit breaker box and plug a different device into that outlet to make sure there is power to it.
If it still does not light up, your adapter could need replacing.
Also check the adapter box for signs of warmth, as it will generate heat when it's plugged in. No heat means no power.
Remove the Battery Sometimes it's as simple as a seated battery.
Remove the battery entirely and clean out any dust, lint or hair that may be clogging the connectors and preventing a proper connection.
Reseat the battery securely and make sure the little locking pins that hold your battery in place are securely fastened and there is no movement.
WARNING: Before you start troubleshooting remember that you are dealing with electricity that can KILL.
http://www.kitchentablecomputers.com/static.php - rules
Only work inside the computer case when the power has been switched off and disconnected. Never open the power source.
Some of the below steps recommend removing physical parts within the computer. While in the computer it is highly recommend that you be aware of ESD and its potential hazards
Check all power and data leads from motherboard to hard drive and all of your cd/dvd drives make sure connections are secure dust free and not faulty
computers need all power and data to travel through every working device and to finish its cycle
so any faulty lead will end in computer error or shutdown / fail to boot or to reboot on a cycle
make sure your computers RAM modules are securely seated with no dust in the sockets also the Cmos battery has charge and seated with no dust in the sockets.
some Motherboards Cmos batteries are soldered in.