If you are unaware of how or where to backup your ESEkeyfile.xml then please follow these steps:-

1. Copy the Keyfile to another location on your Harddrive - (not recommended)
2. Backup the Keyfile by exporting/copying it to an external USB stick (pendrive) - (recommended)
3. Copy the Keyfile to another PC on your network, or laptop - (recommended)
4. Burn your Keyfile to CD/DVD (preferebly re-writable as to not waste a disk.. personal preference) - (recommended)
5. Email your Keyfile to your personal email address - highly recommended
6. DO ALL OF THE ABOVE - most recommended

NOTE:
I can not stress the importance of how vital it is to BACKUP your ESEKeyfile, otherwise you will have to pay 5.50 Euro in order to retrive your details again (hard, long manual process from the Staff)
Secondly, it is just as important to remember your Password matching the registration useraccount!! Thus, I recommend writing the password of your account(s) in a word.doc or text.txt document and including this with your backup Keyfile (zip or rar them together)