i am pretty new to this community as well and had just successfully installed ubuntu 12.10LTS on my winXP as dual boot. on my research, i might have come across something similar to what you are looking for and. based on the little info you provided (partition scheme, ubuntu version, etc), i shall try my best to present the resource that might be useful to your situation.
firstly, i recommend that you find out your partition scheme and type while go through some great resources online or my favourite - on youtube. in a case of information overload, article or manuals can be scanned through to familiarize yourself with the terms that you will encounter as a linux noob like i am.
second, i recommend that you backup all your stuff like what many seasoned computer user always say - backup, backup and backup. there are many backup options that are available theses days and for a laymen like me there is not much security and encryption need especially while figuring out my machine a little better. free services such as CX offer free 10GB storage option while CrashPlan offers (conditional) unlimited backup which i use as i climb up the learning curve
lastly, this particular article may demonstrate the exciting challenges that awaits and when all your data are backed up, you have not much to worry about. its unfortunate that i am not allowed to post more then 2 links due to my lack of reputation - which i found out after completed this entry which had 5 links attached :(
anyhoo, keep on keeping on and although it is not as simple as windows, i believe that it will make me (as well as other noobs) understand computer system a little bit better and what better way (for me) to learn then to try it out in practice. it can be frustrating but you (as well as i am) are in good hand of experts here in this forum which i am very grateful for.