tomwilson74,
I hadn't loaded any maps on my units in a while and I couldn't exactly recall the steps, but I did manage to find an old tutorial I'd originally made when I was at your stage of the game. It's all strung together but maybe it'll help you. Make a copy because it's long.
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Start> Programs>Magellan>Magellan Mapsend Topo 3D, click it>insert Disc #3 of the set into CD drive>When it starts running a Mapsend Warning page will pop up, click Close. Mapsend opens....find area you want to map....look in toolbar for a red square box (that's the region defining tool.....Create region>right click in region, name it, click OK...the new region will appear in the white box on the lower right. Check square box next to the new region's name. Up on the top of the page click Regions>Upload to Gps...Upload Wizard box appears, select Store On Hard Drive...a Checking GPS will ask for the unit's serial number (use the Serial number listed in the GPS's "about" screen or use package serial number but omit first and last digits of that number) click Next...A Converting Regions box will pop up and convert the file....Minimize Mapsend Topo.... Click Windows Start, Programs,Magellan, Explorist , Mapsend Conversion Manager, click it....box pops up, select Transfer Map Regions.> Next... then it asks to either USB connect your GPS or Memory card,....do that.....When the card or unit is found a Map Region selection page shows. Select the region you just created (Note: it should have a .imi extension) Check the square box at the left of the region...click Next...it transfers...Click Next and then Finish. It should have loaded the file to the unit or an SD for the unit.
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Woodstramp - you are our hero! Why can't Magellan make the instructions this simple? We had manuals and user guides spread out from one end of our table to the other trying to make this work before and it never did. Your instructions listed above saved our Explorist 400 from an early death this week. Thanks so much.