How do you turn a normal tv into HDTV?

Standard definition TV's really can't be changed into anything other than what they are. In other Words, there's no conversion kits, etc. But a standard definition TV can still use the digital HDTV signals with the use of a converter box on your antenna system, Dish or DirectTV RF output jacks, etc. The picture, even though converted, will still generally look better than a standard analog signal just because there's quite a bit more information in the signal allowing your analog TV to wowrk at it's maximum capabilities.