Well, my computer is running on a network in a workplace, and the network administrator had installed a program called NetNanny that monitors our internet activity. For some reason, it was blocking the online installer from downloading the necessary files. I contacted the network administrator, and asked him to make an exception for the installers. After he made the exception, out of curiosity, I tried the offline installer, but it still didn't run. Then I tried the online installer, and it ran fine.
I still don't know what the problem was with the offline installer. Perhaps 1.5 Gb was too much for my system to handle. Anyways, the problem is solved.
Thanks again for your help.