All of your data is on your C drive and for normal users they use My Music to store iTunes Library for a Windows user. So if you set it up that way then "YES" all of your iTunes, iPod Apps, Games, Music, Video and Movies are in the iTunes folder in My Music.
If you are using Outlook, then your Contacts and Calender events are stored in your Microsoft Applications Outlook folder...they are .pst files.
Your pictures are stored in My Pictures if you set it up that way.
If you are not backing up "My Documents" as a minimum on a daily or weekly basis then I feel sorry for the day you loose it all with a Hard Drive or other Hardware crash...IT WILL HAPPEN.
Purchase of a 500g external hard drive is very cheap now and will save you so much heartache and us another thread to answer on how to recover what can never be recovered.
EVERYONE...BACK UP YOUR COMPUTERS!!!