I did a bit of searching and found a way to format a microSDXC Card - 64Gb, even on a Windows7 machine...
Click on Start and then click on Run... Type CMD to bring up a Command box and here type in Format /fs:FAT32 driveletter: where driveletter is what appears as the assigned driveletter for the SD card on your machine. Press Enter and you will asked if you want to proceed.
Once you confirm the operation you will see information stating what the current Filesystem is and that it will be changed to FAT32. It will format the card and then verify it which will probably a while - it took nearly five minutes to verify a 2Gb Sd Card!
Once done it will ask you for a Volume Name, just press ENTER for NONE. You will then be given a report. Type EXIT, press ENTER and remove your card.
Plug it in again to verify the format by right clicking on the Drive letter and selecting Properties. Here you should see FAT32 as the File system.
Good luck,
Eric