Well, I may have some bad news for you. There isn't a legitimate application for the 730 by that version number.
The current-- and has been for a while -- is 8.351.
I don't suppose you made a backup of your unit's contents when you first got the unit (hopefully with Explorer) did you?
Here's what I want you to do:
1. Make an Explorer, not Home, backup of your unit's contents now.
2. After doing so, and making sure your backup is on your computer, I want you to go
here and download the proper application for your unit. Use WinRar to extract the contents to your unit and set WinRar to overwrite as necessary.
Once that is done and you have disconnected your unit properly from the computer (using the Hardware Device disconnect icon), then shut down and restart the unit.
Connect to Home and go to Tools-->Latest Map Guarantee. Hopefully, you'll be offered map 840.
If not call support at 866-486-6866. While ebay is not an authorized reseller of Tomtom units, you may get a friendly rep who will add the map to your account.