does it boot at all? you should see the finedrive splash screen, then the main menu for a second or so, then it tries to load maps, how far does yours get?
if it boots but does not load maps or if it gives you an error then you have two options:
one solution is to visit C&C wireless and pay over $100 for a map update or even send them your unit for even more $. see http://www.finedrive-acc.com/shop.cart?action=ITEM&prod_id=F400-08CP
The other solution was to send it to Fine digital but they closed their doors in the US so they no longer support us customers. Because of this I made a DVD with map data I purchased from them before they closed and I added much better instructions; this DVD updates the firmware in the unit and loads the last map data issued to the SD card. you would need a PC with a DVD drive and SD card reader to use it. you can find these DVDs on ebay for $18 which basically covers my costs only.
Now, if it does not boot at all, no splash screen, you could have other issues, if there is an image but no backlight (hard to see but try looking at an angle) and you get responses to key presses, then your backlight could have failed.
if it seems to lock up on boot try holding down the two right hand keys on power up, this should bring up windows CE, if it does you may have a chance at recovering by manually running the repair data I sell to recover the firmware.