If you have a recovery partition, any changes made to your system will destroy access to the partition. You may want to make a complete disk image so you will be able to recover. Do you have recovery media?
Macrium Reflect PING (Partimage Is Not Ghost) (Free alternative to Ghost with more features)
Paragon Drive Backup Express Drive Image XML G4U - Ghost For Unix (Platform-independent, floppy or CD)
DiscWizard (For Seagate or Maxtor drives - contains reduced version of Acronis)
But WUBI or VirtualBox would let you install Ubuntu (or other) without risking your Windows system and the warranty, if any.