Here is some information I found in pursuing the same issue
Both the XP Resource guide and the product docs have
good info -- do lots of reading FIRST (there are many
trap doors you can drop through if you are not careful)
:
One of the most important things to do is
====>>>>> BACK UP YOUR KEYS <<<<<====
Many people have gotten bitten with having their files in
the EFS (Encrypted File System) on a different drive and
for whatever reason, (crash, virus etc) re-installed windows.
If you did not back up your keys, those files are probably
gone -- the SID etc is different if you do a clean install and
the new key for the same user will NOT work with the
files that were encrypted with the key from the previous
install. You have been warned !!!!
In light of the recent theft of the Boeing information that hit
the news, more information on file encryption ...
http://www.iopus.com/guides/efs.htm
http://www.microsoft.com/technet/prodtechnol/winxppro/support/dataprot.mspx
http://ls.berkeley.edu/mail/micronet/2005/0301.html
http://www.microsoft.com/technet/community/columns/secmgmt/sm0205.mspx
http://support.microsoft.com/default.aspx?scid=kb;en-us;241201&sd=tech
http://support.microsoft.com/default.aspx?scid=kb;en-us;223316&sd=tech
http://www.microsoft.com/technet/prodtechnol/winxppro/deploy/cryptfs.mspx
http://www.microsoft.com/technet/prodtechnol/winxppro/maintain/sharefilesefs.mspx
http://support.microsoft.com/default.aspx?scid=kb;en-us;259732
http://support.microsoft.com/default.aspx?scid=kb;en-us;290260