If you purchased a sonar unit in 2000 or maybe earlier, did you know that there are upgrades for it? Yep, there are, just go online to the maker of your unit. Be sure to check your unit and see what the last upgrade on your unit was. Then download from the manufactures the next upgrades after the one on your unit. I have a Lowrance and my last upgrade was 1.7.0 (upgraded in July 2007) and they currently have a 1.9.0. According to a friend (turfman) you can use your Lake Map chip for this upgrade or you can buy a new chip and download onto that and then download into your sonar unit. You will have to buy a device for the chip holder, about 12 to 13 dollars at most outlets, to download the data. The foregoing method of upgrading is a lot cheaper than buying a new unit. If, you are like me and don't understand how to do it (ThaBear did mine), get a friend or one of your children or grandchildren to do it for you, it really makes them feel special to do something for you and they are. If I omitted something, I'm sure someone will offer us additional advice and it would be welcomed. Also, some companies will download the lastest editions for your unit, if you will mail them the unit and pay for return postage. Be sure to check and see if the manufacture of your unit has this program.