|RAM has nothing to do with the hard drive. It appears your system has 1.5GB RAM.|
Are you going to run Windows on the new drive or is it strictly for storage? The larger the drive capacity, the more platters. The more platters, the more heat & noise. And more parts means more things to potentially go wrong. I believe 2TB drives use 4 platters, 1TB drives have 2 platters. Do some research before you buy.