Window vista or xp is not detecting my third hard drive

Hard drives are blank and have to be formatted... before an OS can see them.

Duh! I have should of know that. Thank You r-sky.

There are instances when they aren't formatted properly and need a special "Drive Eraser" program. Oddly, none of the hard drive manufacturers provide this.

A drive i had was added as a second hard drive then I decided to use it for Windows. I couldn't use it and reformatting did nothing. After overwriting all data (no format at all) with Drive Eraser I could then format.

Always format in FULL NTFS. Full takes longer but it's building up a bad sector table which you should always do. I believe there should be no quick format option.