Excel Recovery: Encryption-Protected Files
The best choice would probably be to employ an offsite backup program, where files are securely stored on a remote server or drive. If your local files become unusable, they can be recovered from that source. Mozy and others offer unlimited online backup for about $60 a year. Not much more than that would buy an external hard drive for the same purpose.
If your encrypted workbook has been corrupted and or deleted, a file recovery program is going to be required. There are a number of programs available that will recover lost or corrupted files. Some are for free, but if you have gone to the trouble to encrypt a file, it would be a wise decision not to trust a shareware program due to security concerns.
Programs for purchase start at about $40, but you will want to ensure that the program will recover all the elements of the workbook. This is another reason to avoid freeware or shareware; some will only recover data, not names, labels or formulas. They use differing strategies from kernel recovery to time-stamped backups as a basis for their recovery process.
Planning ahead will help remove the specter of having to deal with lost passwords or files. Use of a backup strategy along with an uninterrupted power supply will all but eliminate the causes of corruption not related to a malware attack. Developing and using a formula to create passwords and a safe-keeping place for your passwords will make your Excel files secure and accessible.