You're not going to get anywhere here (other than PC advice). You should report the guy to Ebay and get your money back. Next time make sure you know what you're buying regardless of what people say. People who know about computers would see a Pentium 4 listed somewhere and then if they read that the seller says that it's "powerful", they would laugh and walk away. You simply didn't know what you were doing. Take the proper steps and make a report.
Asus Laptop: K53TA
OS: Windows 7 Home Premium, 64-Bit - SP1
CPU: AMD Llano A6-3400M, Quad-Core, 1.4GHz-2.6GHz (Overclocked)
GPU: AMD Radeon HD6650M, 1GB GDDR3 (Catalyst 13.1)
RAM: Samsung 4GB DDR3-1333
OS: Windows 7 Home Premium, 64-Bit - SP1
CPU: AMD Llano A6-3400M, Quad-Core, 1.4GHz-2.6GHz (Overclocked)
GPU: AMD Radeon HD6650M, 1GB GDDR3 (Catalyst 13.1)
RAM: Samsung 4GB DDR3-1333