My son has a Windows Vista PC in his room, and I want to login has him so I can see what he is surfing.
His account has admin rights, and mine has too.
Is there any way to do this without resetting his password?
Acces different's user internet temp folder.
IF Win7/8 Tools >> Folders options >> View
Check "Hidden Items"
Internet Explorer: C:\Documents and Settings\USERNAME\Local Settings\Temporary Internet Files <-- XP
C:\Users\USERNAME\AppData\Local <-- Vista++
unless you want to work with his files to track stuff (as bZezzz and EBGreen suggest), yes you will have to reset his password to login as him and load up the browser to check the history. if it was easy to do what you suggest, then their user security would be meaningless at best.
since you are an admin on the box, look at l0phCrack, to get his current password. keep in mind though, regardless of your personal feelings on the matter this is 100% a jerk move, and teaching a child morality by being immoral is problematic at best.
Check out Kon-Boot. With it you can log in as any user without knowing or changing the password.