I don’t see how.

Maybe .

you are just sharing the signal, not folders and stuff

please don’t be using comcast, ‘cuz then he could

Only if you allow sharing - or if he’s very good at hacking.

It is possible, but generally you can’t do it without configuring each computer to connect to one another, changing firewall permissions and things like that. If his laptop or your computer can view each other from within My Computer then you’re configured for it but if you can’t see anything new then you are fine.

Only if you put them in your Shared Folder. Go to your Network Connections, right click on your wireless connection, click properties.

Disable 1) Client for Microsoft Networks and 2) File and Printer Sharing for Microsoft Networks, to be extra sure.

Yes, any information on your computer can be seen if you are connected to a network if someone else is also connected to the network. their are a few ways to protect yourself.

1. Do not broadcast your signal: Even if you do this anyone trying to get into your network that knows anything will be able to with no problem

2. Secure your network by using WPA or WPA2 encryption: Using WEP is easily bypassed.

3. Make sure your Firewall has all the proper setting turned on: This will further prevent anyone getting to your information by adding an extra layer of protection. For example, if they are in your network they still have to get passed your firewall.

There are other things but those are the basics.

You can disable his ability to download and view your files by disabling file/print sharing under Network Connections in the Control Panel. As far as viewing your browsing activity, that could be compromised quite easily. It depends on his level of knowledge. You can protect against that by using a web-based proxy server that would forward your http requests through computer(s) located around the internet, and all he’ll see is your ip address connecting to the ip address of the proxy server. Your internet performance may suffer, though.

Any computer using a wireless network can be hacked it is just a matter of finding the backdoor to the files. To prevent security problems you need a secure file encryption program I do not know of any right now.
In the meantime security software such as a firewall, anti-virus utility, anti-Trojan utility, anti-key logger utility, are just for starters. Look around the security software section and they can recommend some stuff that can help keep you safe from the nastiness out here on the internet.

Yes it can be. Your privacy can be compromised if you connect directly to the Internet also. If you secure the router properly, you are safer using a wireless router than not.

Sure method to prevent compromise of your system. Don’t have one.
It’s the only 100% effective method.