...installation. My username and passwd will not work.What can I do now???? Installation was done on my laptop. I have made many attempts at signing in, but to no avail. It keeps telling me that the username/password is incorrect. ??????

I don't know if Ubuntu install disks have a system rescue option but most of the rest do. You need to boot a system rescue disk and mount the partition you installed ubuntu to. Drill down the directory tree to /etc/ and edit the passwd file. Find your user entry. user_name:delete-this-junk:delete the junk between the two colons leaving the colons.Reboot and login without a password.

The user name is rootand password was that, you have provided during installation