start up by going into the control panel and the user accounts screen. make a new user that is an administrator. then change your existing one to a limited account. that way you won't have to set up your shortcuts, documents etc again. use the limited one as a matter of course and swap into admin for installing software and making changes to windows etc.
if you want to be a power user you have to fiddle a little more.
go into administrative tools in the control panel. then go into computer management. in local users and groups select groups and a list will appear in the right hand column. double-click power users and then add your limited account by clicking on add and typing the name of your limited one.
i have three accounts. the main one is a limited one, found in computer management under 'users'. i use this for work, the net etc. i have a power user one for running non-xp compatible stuff such as old games. and finally i have an admin one solely for installing stuff and fiddling with windows.
have fun