To have an easier access to the computer I deleted the user's password so it is blank. But now I'm still asked to type in a password for sudo actions such as installing programms, etc.

I know that this belongs to Ubuntu's outrageous security policy (which is why I use Ubuntu in the first place..) but I don't have any password to enter any more!!

The old user password is not accepted and anything else (like just hitting enter) doesn't work either. I already tried the recovery mode (root shell) way

passwd >USER<

but it replied that it can't access the password or it has no authority.

Thanks in advance for your help!