this will stop some but not all. some get in and operate with "system" privilages. you can not do one thing and consider your self safe. you need AV and Firewall software along with all the security tweaks you can find.

i really recomend downloading the cleaner. not to check for trojans so much but because it comes with a registry checker that does not allow unauthorized changes to the registry. even if you get the trial version the reg checker stays working even after the trojan cleaner expires