Do you have a password reset disc around? Or perhaps another administrator account on the system?
You could 'restore your system to factory defaults' if it comes with a recovery partition or similar, but of course this means you will lose all your data and programs installed currently.
You say you have tried booting from the disc on startup, did you edit the BIOS settings? Are you sure you have a bootable upgrade disc?
I am not sure if upgrading removes your password, if it doesn't, you'll still have the same problem.
You may have a hidden administrator account you could access, to reset passwords. Try booting your system in safe mode (press F8 then select safe mode), select the administrator account, it may have no password by default (if it is enabled and if it hasn't been altered).