Your password will be unchanged. i.e. the same as you had with 8.04.

At prompt type sudo apt-get -f install

It will ask for your password, but just use what you had before when you
tried to upgrade. It should give you a list of applications it wants to
install. Just say Y and cross your fingers.

When it is done you can type login. Give your user name and password. Then
type startx

If this fails then you can try to complete the upgrade with these
instructions: https://help.ubuntu.com/community/EOLUpgrades/Hardy

Personally I would never have attempted the upgrade and would backup and do
a fresh installation. It is not too late and can be still done.

My reasons for this are major changes from 8.04 to 10.04: grub to grub2,
ext3 to ext4, upsplash to Plymouth, old video drivers to new which rely on
kernel mode setting (which may be why you do not get a GUI), old kernel to
new, and removal of HAL. There is just too much to go wrong, IMO.