emergency - lost identity

[Arthur Dyck]

I seem to have lost my user identity and password and su access.  Is there any 
way of restoring these?  I am using Kubuntu Dapper.

When I try to go into Users and Groups go into Administrator Mode, I get "Su 
returned with an error"

The diagnostics is:

Possible reasons:

An error occurred during your last KDE upgrade leaving an orphaned  control 
module.

You have old third party modules lying around .

Check these points carefully and try to remove the module mentioned in the 
error message.  If this fails, consider contacting  your distributor or  
packager."

If need be, can I reinstall Kubuntu while leaving my data files intact?  I am 
trying to back them up but K3b has frozen and I can't even get my CD drive to 
open.

Arthur