My laptop previously had 2 slots of RAM ( 1x1Gb , 1x2GB , both were clocked at 1066mhz) and it was working on windows 7 x86 OS. I Upgraded the ram with ( 2x4GB clcoked at 1333mhz). Bios displayed 8192MB of memory and windows was working ok but (only 2.99GB of ram from 8gb was avabile). So i decided to switch to an x64 system to be able to use all the amount of memory. But the laptop wasnt able to install any os (windows 7 x64 or windows 8 x64) so i placed the 3gb of ram instead of 8gb. Then i succesfully instaled an x64 os (windows 8). After than i placed the 8gb ram back again. Now the computer doesnt boot in the os but bios is working normally. I tried also to install ubuntu , without any succes. What should i do ?? All the help will be appreciated. thanks