NO. The hard drive (hdd) stores your data and the operating system, and is responsible for your being to turn on the computer. Think of it as your brain (though the CPU is kinda like your brain too). The dvd drive is an optical drive that lets you read/write CDs and DVDs (kinda like your eyes and hands). LOL, sorry if the comparisons are a little off.
Hard Drive and DVD/CD Drive are different components in a PC, if your hard drive is fried you DON'T need to replace you DVD/CD Drive....so dont worry about your DVD/CD Drive at all
NO NO NO NO NO! They are two completely separate hardware. The item you replaced was the internal hard drive. It stores information necessary for the operating system to run. It also stores files like you moves and music and games. The DVD-ROM drive is the device that reads DVDs and CDs and it runs the content on the discs like movies, music, or documents. Two totally different things. The reason they sound the same is because the operate alike, using an electric motor to spin them in a circular motion.