PC question

[skeeter@ccia.com]

I want to sell my old computer. There are about $4000 worth of games, programs etc installed on it I don't want to loose. Since I do not want the new owner to gather information such as my bank numbers, websites visited, log in information, passwords etc or any other personal information that might be on it, is there a free program I can wipe the hard drive clean without destroying the programs installed on it? Should I just remove the hard drive and install a new one? Would this remove personal information? Evidence wipe is about the only program I have found that will clean it enough to sell but I think if I use it I will have to buy a new start up disc. Any suggestions? I don't want to spend the $100 they want for an eraser....any free downloads?