How to restric the user to accessing the s/w on the system

i am developing one application in which

1) i need to fetch the user name from the computer how currently log in

2) i need to fetch the all application which is install on the computer for example in the computer they install Ms.Net,Ms Office etc

3) i need to restric the for accessing some install software in the computer for example if developer user sign in i will give all permission if suppose any network people or some guest user loggin i want restric them to accessing Ms.Net software or some other software

The above three are my question out of 3 i have done first 2 that is fetching the user name from the computer and fetching the software install on the system but i am unable to do the thired one

can anyone help me for doing the thired question

please please please help me