USB Formatting issue

Hello,

I am working as a teacher in China. I use PPTs in class that I make on the desktop PC computer they gave me, I also have my laptop from home, but I don't have the powerpoint program, so I don't use it for lesson planning. The school computers are both slow and often filled with viruses, so when I bring the USBs back to my apartment I often reformat them. One of them was having too many issues and the PC said it could not reformat it, so I used my macbook. I used Disk Utility with the settings of Mac OS Extended (journalled) with the security option "Zero Out". Then I tried to check and see if anything needed to be repaired. It said "Volume Header Needs Minor Repair", "The Volume was found corrupt and needs to be repaired" then it says "Disk Utility stopped repairing" and "Disk utility can't repair this disk, back up as many files as possible, reformat the disk, and restore your backup files". Then the details say "The volume could not be repaired".
Now the PC doesn't know what to do with it and still won't reformat it, but says it does not have anything on it.

What do I do now? I'm really frustrated and this is a 64 GB drive. It's especially frustrating because it seems like my problems are caused by my own computer.

You need to format the stick as MS DOS format (FAT) for it to work on both a mac and PC

Also any PC viruses at your school are incapable of infecting a mac, so constant reformatting isn't really needed.

Also, on another note, if you ever need to edit POwerPoint files on your Mac, and cannot afford a copy of Office, then the free Libre Office will let you do that

http://www.libreoffice.org/download/

I know it can't infect my laptop, but the viruses can't be left on there. The one that forced me to format was corrupting all the data, and since I go from one class to another it gets to infect the next computer I use.

"You need to format the stick as MS DOS format (FAT) for it to work on both a mac and PC"

It was working on both before, but now it won't work on either and I don't know how to format or anything. The stuff I've done so far has been following directions I've found on other posts, I have just enough computer intel to get by, but not enough to know how to do most stuff without step by step instructions since I tend to learn only when I need to do something.