Learn about Windows PowerShell
Summary: Use Windows PowerShell to find the largest file in your user profile.
How can I use Windows PowerShell to find the largest file in my user profile?
Use the Get-ChildItem cmdlet (dir is an alias for the Get-ChildItem), do a recursive search of your user profile directory, then sort the files by size and select the last file:
dir $env:USERPROFILE -Recurse -File | sort length | select -last 1