Your card is 64GB and formatted as exFAT but windows XP does not recognize exFAT because XP is to old but with this updates it will recognize it.
Download Update for Windows XP (KB955704) from Official Microsoft Download Center
SD cards larger then 32GB have to de formatted exFAT because the old standard FAT32 can not format SD cards larger than 32GB.
Formatting a card in the phone gives the best change that you new phone can read the card.
But coping 45 GB will take some time but then you have a back up of your data.
If you however already have al the data which is on the card on your PC you do not have to copy it.
If you put the card in your new phone before you switch it on then the card will be formatted during the setup. (but i am not 100% sure) and if you use the backup then your apps will be placed back on the SD card and after that you can copy back your data.
Hope that someone can confirm my story.