If your drivers are correct, you should be able to access files on the phone with file browser on your computer when the two are connected via USB.
Zune does not support Windows Phone 8 and above. XP is out of service life and should probably be upgraded. Windows 8 (desktop) and higher have an App for connecting with Windows Phone.
Try safely ejecting your SD card; Storage Sense > SD card > safely remove. Power down and remove the card. Boot the phone, visit Storage Sense and let it finish scanning. Soft Reset (hold Volume Down + Power buttons until reboot). Power down again > insert the SD card > power on > Storage Sense > SD Card > let Storage Sense read the card. This might shrink Other if more files get recognized during the card scan.
FWIW - a trip to the Desktop App for Windows Phone usually helps this process of rescan and index of cards. I find that my Storage Sense reads the contents of my card properly after it plugs into the desktop App. If you have a friend with a Windowss 8 or higher box that will let you have some time on there - you could try the Desktop App.
As Harrie-S says, some of the Other files may be ones you actually want to keep.