did you buy the hard drive new or did you format a previously used hard drive? if so, what did you use to format and what file system did you format to. ie. fat32, ntfs, ext3 etc..?
also, are you new to linux? if so then debian may be a bit of a wrong choice. debian is designed for more advanced users. mandrake is aimed at new users. it is user friendly, so everything is explained while installing. also it partitions your hard drive for you. maybe you should try this out first.