can I feel safe with windows 7!?

hi!

not long ago a friend of mine who unlike me does profess a lot of computer knowledge told me that if someone has my ip address they can gain full access to my computer with relative ease while other knowledgeable people have told me it is very hard, it still bothered me and I havent quite been able to shake this since an ip address is not exactly hard to see, heck anyone I have ever send an email to has it!

I am sure this noob question has been asked many times and I did try searching :) but I will try asking this anyway hopefully someone will answer.

I am running a clean install of windows 7 pro 64bit with microsoft security essential and sitting behind a router. I dont run any suspicious programs like cracked games or such, I dont think i surf into suspicious websites, I do keep my os/av uptodate and I have UAC turned on to max.

so my question is can someone just using my ip address hack into my computer? and if so how easy is it? I mean is it enough that some script kiddy ( term? :P ) downloads some hack tools and starts hacking ( sorry I really am clueless I know! ) or would the person require some really impressive hacking skills/hardware that is very rare?

also is there a way I can make my windows more secure?

Thank you both for replying, well I did read Dan Wagners advice and from what I can see there are two things he pointed out where I fail

1. I do tend to leave my computer turned on quite a lot, I will from now on use the Lock function when i leave my desktop or is it safer to simply turn my computer off?

2. I dont use a third party firewall as I was told before that windows firewall is very solid in win7? also I was told that third party software sometimes come with their own security holes something that might not happen with ms own product since they prob know the OS better? Also it is my understanding that the isps usually block suspicious open ports that are not blocked by default by windows firewall? but then again i am not exactly an expert and could be wrong so do you think ms firewall is not enough and if so could you explain in newbi terms why?

DocBrown said:

A router can also add an extra layer of protection

look at nabman´s first post above: "I am running a clean install of windows 7 pro 64bit with microsoft security essential and sitting behind a router."

thank you yes as hackerman1 points out I am sitting behind a router provided by my ISP, a router that they claim is very secure and has its own security ( whatever that means! ) so that point should be covered.