In about 1 year, your existing analog TV tuner will be obsolete. The federally mandated switch to digital TV is scheduled for February 17, 2009.
Your existing TV will only continue to work if you connect it to some other video source like cable, satellite or you buy a new digital converter. Of course, you can also buy a new digital TV too.
Some help is on the way. Coupons for $40 to purchase the converter boxes will be sent to each home this winter.
More information on the digital TV is available from the government site, http://www.dtv.gov/