No, unless you have your pc set to receive files through sharing. Look in your advanced sharing settings, and only if you want, you can turn off file and printer sharing. There is a password setting on it so it makes it harder for people to break in if you have it enabled in the same sharing settings window. Here is a screenshot so you can see what it is:
Default is set to share, but the password is enabled. Even in sharing, most of the time they cannot give you anything (viruses, files, etc) unless you set the folders to be able to be modified. Sharing can be good with password enabled, as you can use printers or connect to friendly computers without having to use storage from somewhere else on the internet.
On the flip side, if you are using a stranger's Wireless network, they are able to give you viruses (however, this requires them to have some kind of sophistication and a deliberate desire to infect your computer). That is why you don't "barrow", or steal rather, someone else's wifi