It depends on what data you wish to encrypt; when and where. If you want to store your data on the PC in an encrypted format you might consider TrueCrypt http://www.truecrypt.org/
. It is simple to use and you can share the data with Windows provided you build a TrueCrypt container file in a location accessible to both Linux and Windows.
You can also choose to encrypt your home directory when you install Linux. I am not sure if or how that can be done after installation. But now I am curious and will let you know if I figure out how to do it.
If you wish to send encrypted email you might use the Enigmail addon for Thunderbird. I think it may support other email programs as well.
Please tell us a little more about what your are trying to do.