problem installing 8.1.3

Hello:
I need help with installation
I'm working on a XP Pro box, and trrying to install postgresql 8.1.3 from windows installer. I always installed previous versions without a problem, but recently I've made some changes to user permissions, and now I´m getting this error message:

"failed to create process for initdb: Logon failure: the user hasn´t been granted this kind of logon on this machine" 
(may be slightly different because I have a spanish version of XP and this is my translation...)
the original message in spanish is:

"failed to create process for initdb: no se ha concedido al usuario este tipo de inicio de sesión en este equipo"

I tried several times, even I gave the user "everyone" permission to the Program files folder, I deleted postgres user before reinstall, but I always get the same error and the installation process is rolled back.
Can anyone help me?
Thanks in advance

Sergio

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