Why is Windows 7 more secure than Vista and XP?
Standard Mode is a new User Profile in Windows 7. Standard mode allows users to still customize there own profile, but will protect against any security modifications. Any changes to system security (UAC settings), Protection programs modification (anti-virus/security programs) the user will prompted for administrator approval.
The only problem with standard mode will be convincing users to actually implement it. Here is an article in Technet magazine by Mark Russinovich that explains it further.