File Scrubber Question?

I have a laptop that I want to lend to someone to use. I have deleted all the files but I KNOW they are not gone - gone. I am looking for a shareware/feeware file scrubber program that will overwrite those files without wiping the disk (I do NOT want to reload the OS and all the programs). This laptop is running Windows Vista Home Basic - 32 bits. Recommendations please?