How to Enable DEP for certain programs only.?

I am running windows vista home edition and i want to enable DEP for some programs while leaving others alone. I know how to get to the options, but the problem is that my options are greyed out. It says that i need to be a computer administrator and that i need to use the bcdedit.exe file. I am not sure how to be the administrator (I am the only user on this pc). I know that DEP is Essential to the security and i have a security software, but i still want to be sure that i dont get screwed over if i do get a virus. Please help.