I am thinking Windows should have two different privilege user account for one user. One account will be a limited privilege account and is used to browser the web and get Emails. the other account should have administrator privileges. Two account only needs one time logging in.In order to access two accounts simultaneously( no logging off, or switch involved), there should have two desktops for each account on one monitor. a user can freely switch between his/her two desktops.In order to display two desktops at the same time. the second desktops can be created by uisng remote desktop technology locally. that means the remote desktop server and client programs are installed in one machine and these two linked locally.because a user has two desktops ,the limited desktops can add any security features and make it much safe and not password input required when doing the surf.any comments are welcome.

That's basically what User Account Control (UAC) is. Except that it operates without the need for separate desktops.

the benefit is much greater than UAC, two accounts for one user gives the OS an opportunity to set strict privileges for one account. that means only IE and Outlook can be executed through this account, any other programs will be prohibited. User-installed program will be executed on the other account. this will get full benefit from the UAC. any programs in the Internet will be prohibited to run.

give that goal you stated then you can create 2 accounts but with2 names.

with 2 names, how the OSs knows that 2 names belong to one user? if not, the user has to log in twice to have his 2 account created, not convenience.

I understand but that the way it work now you caould have a local account and a domain account