vista home premium. existing account, password lockout

I am trying install 8.4 and i already have an account that i can not remember the password.

Whem i try to.... go to admin tools>comp management there is no local user and groups option to delete the user (managed through user accounts on this version of vista).

When i try to run... net user postgres /delete i get access is denied on the admin account

I realize this is more of a vista question but was hoping someone could help out. Thanks for reading

(1) Open the Start menu, and type lusrmgr.msc in the search line and pressEnter.

NOTE: This file is located at C:\Windows\System32\lusrmgr.msc.

(2) Expand the 'Users' folder

(3) On the right hand side of the screen, you will see all the users defined on the system.

(4) You can right click on the postgres user name and choose 'Set Password' and
then change it to something else OR You can delete the user and then have the installer recreate the user.

Regards,
Raghu