Can i detect if someone is viewing my pc through remote desktop software?

my wife installed one of it in my pc (team viewer 6) and i saw her chatting with someone through it about online money earning sites, the one she was chatting with says "please wait im currently checking ur pc right now" ...i dont how it works but, i know it doesnt sounds good. i uninstalled that software, but as said in their chat seems like my pc was already scanned by someone, so anyone here knows anything to block it someone is trying to scan through your pc? and is there anything i could use to prevent others from installing softwares in my pc? i know i could use the administrative account to set password on my pc but i dont like it asking for password during boot up.