After I put in a new ram, there is a problem with my cd-drive. The LED light in front of the cd-drive keeps on blinking but my computer could not detect it. (The cd-drive is not listed in the device manager.) I can also hear the sound of the cd-drive actually working. I tried to stop it by pushing the eject button but it didn't respond. Please help.
Doesn't really make sense, but you can try a few things.
Have you tried to removing the extra RAM and see if the drive works again? You could also try to unplug and replug both power and SATA (or PATA) cables from the drive and motherboard. Sometimes, when you open the case, cables get moved a bit and might not make contact properly anymore; happened to me once with a SATA HDD.