Here is a tip to get you out of trouble if you have a corrupted SD card. I was transferring some routes to my Tomtom 550, I keep all of my routes on a micro SD card so that they are safe in the event of a factory reset.
So, the other day plugged in the Tomtom to the computer and the SD card that was definitely in the Tomtom was not showing up on the PC. I took the card out and put it directly into the PC and there it was working fine. For some reason the Tomtom would not recognise the card. Sometimes the cards get corrupted when taking them in and out. I tried formatting it on the PC put it back in the Tomtom and no dice. I was about to order a new card when I had a light bulb moment, there is obviously something on the card that the PC likes and Tomtom doesn't, having already formatted the card a few times with no luck, I thought I'll put it through the shredder (not a physical shredder), a PC file shredder. I set the shredder to maximum shred to completely wipe the card then reformatted the card again on the PC and Bob's your uncle all was working again.
So if you have a corrupted card or memory stick try the shredding trick first before you dump it.
