You can always create a non-admin account for "normal" use. Set your admin account so that the password doesn't expire, and make sure you remember that password, because you might not use it for a while. Then create a new account that is "limited" (or create a NEW admin account, then change your old account type to "limited" so all your settings are still intact). Once you have it set up, use TweakUI (http://www.microsoft.com/windowsxp/downloads/powertoys/xppowertoys.mspx) to set up the account that should login automatically.

If you're on your "normal" account and need temp admin rights, use runas to run a program with admin rights (you remembered that password, didn't you?)