Administrative Problems With Windows 7?

Hi all, i'm trying to fix my nans netbook but i am not familiar with windows 7, basically, every time i click on an application it comes up with "open with" and it doesnt always open the apps as administrator as it should, a warning message pops up instead of any program, really all i need to know is what to do, either re-boot the system or system restore as it is not really good for me as i am not familiar with the system, also i am currently scanning the system with AVG free edition and so far it has found 2 trojan fakes, they may be a problem, any answers apreciated, thanks, camron.