Password issues

I have a Power Mac G5 2.0 processor that i installed Leopard onto. I did not put a password in the OS during installation but now when i try to do a Mac software update i get asked for a password???????!!!!! i don"t get???!!!
Is there a way around this. i can recall a time where on other occasions I booted from the install disk and seeing an option for " Password Reset".
Help.... what to do ?????!!

 

Heres what i did. i booted from the Leopard installation CD and went to disk utilities/password reset and created a password, saved it and rebooted. When prompted at start-up for the password, i entered it of course and as was well. When I did my software updates again i was prompted for a password, entered it and all was well.
That was a couple of days ago but today when i start the G5, all i get is a blue screen, i can see the mouse but thats all. The G5 never completely boots, it just sits there with a blue screen!!!!!!!!! What happened ?????!!!!!

 

It was suggested that i boot from the OS CD( Tiger 10.4) and do a Disk repair so I did and all seems well. It was also recomended that afterward i boot into SAFEBOOT which I did, but like a dumb-ass i choose the option to " List Name and Password" option at boot up. But like a moron when i created the user name i decieded to be clever and did something like
" APPLE G5 ! ( appleg5)" at least thats what I saw when i booted to the OS disk and did a password reset. But i don't remember how many spaces i put between APPLPE and G5 and Exclamation ! ARRGHHH!!!! and i think that is why the log in box is shaking its head. saying "No".. What to do now????? DAMM very frustrating !!!!!!!?????