How can I fix this error

Unplug the device and remove the battery. If possible, remove the memory access door on the bottom of the laptop. It should be a compartment about 3 inches by 3 inches, otherwise you need to remove the entire bottom cover. Once you remove these screws, you should see two stacked boards, called SODIMMs. This is the memory. Ground yourself by touching any metal component inside of the case, like the optical drive. Now, pull the two tabs on either side of the memory away from the memory at the same time, until the memory pops up by itself. Pull the stick of memory out at a 45 degree angle, with very little force needed. Now, do the same with the bottom stacked SODIMM. Now, at the same angle that it came out, put the SODIMM back in, pushing it in all the way, then down flat until the two tabs snap back into place. Do the same for the top SODIMM. Replace any covers that you removed, reinstall the battery, and try to turn on the computer.