How do I fix plain blue screen on my lenovo laptop?

Blue screen of death. You need a pro.

Does the Blue screen happen immediately after you turn on your laptop or does it do something else before that? You have to be specific.

Look on the microsoft site - plenty of answers there

Get a new lap top

Get a bootable copy of Ubuntu and see if the computer will load it. If so, your windows operating system may missing.

If you have waaranty call lenovo and talk about it. If you don't then you can take it to a computer shop. Could be something as simple as bad ram. But can also be the motherboard. If its the motherboard its probably not worth fixing unless its some high end expensive laptop.

We need a bit more information, which operating system? Does it past POST? Can you get into the BIOS?
Initially try a BIOS reset. Disconnect the charger, remove the main battery and if possible the CMOS battery. Hold down the power button briefly. Then reassemble. Try again.

Start again and tell us the OS. You could tap F12 at system start to intercept the bios boot menu just to see if has got that far. Ctrl-alt-del is obsolete and won't help you one little bit. It may also be possible to start it in safe mode. See link.

Read article about troubleshooting BSOD

While one thing for sure you have to clear your BIOS by removing your Graphics card, remove the battery and press and hold the power button down for 20sec to remove any lingering power stored in the device. Connect the DC power brick and press the power button again. You will hear a high pitch tone of 80 db. Power down the device then Reinstall the graphics cards and battery leaving the access plate off because you may have to repeat this a couple of times before the BIOS reprograms itself. Press the power button while holding the Windows key down at the same time. A Systems Check screen should appear on the screen if you made it to this point. Let it finish running it's course before replacing the access plate on the bottom. Note: make sure you pay close attention to the (DST) Drive Self Test in Systems Check to make sure that your hard drive has not failed because it won't let you know if it's the hard drive that needs replacing. If not Repeat the entire process if necessary.