I've encrypted some of my files with EFS in Windows XP. Then, after reinstalling Windows XP I (of course) can't access my info. What can I do to recover (decode) these files.
Thanx everyone who can help!

S.O.L. unless you have a backup of your private key from the previous install.

Thank you! And howto backup private keys (for future ?

First log on as the default local administrator account. This account is known as the recovery agent. This account can decrypt any encrypted file from any user on that computer.

After you log on, make sure you go ahead and encrypt at least one file with this account, to ensure the creation of the EFS certificate.

Next, go to the Start Menu Run box, type certmgr.msc and press Enter.
In the Certificates console that comes up, browse to Personal-->Certificates and select the Administrator certificate in the right pane. If there is more than one with the same name, select the one with the latest expiration date.
Right click the certificate and select All Tasks-->Export.
Click Next, select "Yes, export private key", then click Next again.
Select "Include all certificates in the path", "Enable strong encryption", and make sure "delete the private key" is NOT selected, then click Next.
Enter a password for encrypting the private key. Use a good password (not blank or "password" or too short), and do not lose the password! You will need it if you need to recover the key later.
Next type or browse to a location and name for the pfx file, which will be the exported certificate. Put it on a floppy.
Click Next, then Finish. Make a copy of the floppy so that you have 2, and keep them in separate safe and secure locations.
Remember, if someone gains access to this key, they can decrypt any of your encrypted files!

If you need to import (recover) a lost key, just double click the pfx file to start the import wizard, and follow the steps in the wizard. Or you can start the wizard in the Certificates Console by browsing to Personal-->Certificates, right-clicking certificates and selecting All Tasks-->Import.

Test your backup to make sure it works when you are done. There's nothing worse than false security!