When i power up my cf51 it doesnt boot.

replace your power supply you have lost your 12 volt supply coming from your power supply
but you have your other power supply voltages still working

check to see if all the connectors are plugged in properly

The problem maybe the RAM, it is faulty or just needs reseating to make proper electrical contact.
Reseat the RAM and then boot up your laptop. If it still does not boot up then remove the RAM module/s and take them to your friendly computer repair shop and get them to test the RAM for you. Just like you sometimes need a mechanic to repair your car, sometimes you do need a technician to diagnose and identify the fault or faults on your computer. Not only does a good service technican have the experience to deal with this type of problem, they also have the equipment that allows them to look at things the average computer user can't see, and he has a collection of replacement parts that can be used to quickly test individual components on your computer.

Try this:
tap F8 on boot and go to safe mode with networking. If you are unable to load the OS is seems as thou you have a corrupted OS and will have to reload it. I hope you have backed up your data and have a recovery disk.

Remove the Power Cord, then press and hold the power button for 30 seconds. After 30 seconds, plug the cord back in and press the power button. If it works, you had a Static Charge Buildup that had to be released.

Remove the Power Cord, Open the Case and remove one of thememory chips. Set the chip aside then try rebooting the computer. If it boots, then you know the memory chip you set aside is bad so mark an x onit with an ink pen. If it fails to boot then move the chip to the nextmemory slot and try rebooting. If it fails take the chip out and set itaside, then put the other chip in and try booting it in both slots. If itboots, just to verify that the chip set aside is bad, mark an x on it and putit into the open memory chip slot and try booting.If the above two steps fail, pull the main power plug that comes out of the power supply and plugs into the motherboard. The end that plugs into the motherboard is probably about two inches long, Grab the release latch on it and press it while pulling up to unplug it. Wait 30 seconds then plug it back into the motherboard. Push it back in firmly.
Try turning on the system.

From your description you have a motherboard issue, the only way to rectify this, it must be replaced.

remove charger,
remove battery

press and hold the power on button for 1min

place battery

press power on button,

if it doesnt light up, then check your memories chips. try another one

good luck

the problem is its a lcd liquid crystal leak you need to replace the lcd you can get them from dell.com

Dear Friend,
After studying your case i feel that there is problem with your hardware may be mother board so before doing any more RND its better you show it to the Service Center

Hi there
Try taking the battery out and power it on AC only, post back with the results.

Good luck