When you login with your username & password into sharepoint (2007) site, it displays as a "System Account" instead of your username or full name on the top right corner of the website. What ever changes you make inside the site, for example upload a file, post a comment, sharepoint marks it as a System account instead of your name.
To fix this, you must run the following commands:
stsadm -o updatefarmcredentials -identitytype NetworkService
followed by:
iisreset
Because your account was used to create the SharePoint databases, your account is marked as a System Account. You need to run the STSADM command "updatefarmcredentials" and set it to an account like the NetworkService account to prevent this from occurring.
Sree