Hey brother, plz specify for wich need/purpose u need such a big capacity HDD and that too a 500 GB one !!!
Yes, 500GB HDDs r present but the cost sumthing like a cool 500$ (USD) in the US markets... (if i am wrong abt the price plz correct me guys!) so if u want that much space u can losen up ur wallets ever so happily...
but on a serious note..... a 160GB HDD would be more than enough for HOME use unless u r planning to keep DVD MOVIES on ur HDD or a lot of songs and media/movie clips.....
cheers n peace.....