Only one partition in Vista... i want more.. how???? plz help

hi... i have only one partition C: of 160 GB with vista installed.... vista's inbuilt disk management dont allow to partition C: because its a root partition... Partition Magic doesnot work on Vista... How can i have more (i want 4) partitions by redistributing the space in C: drive.... by the way when i use XP and install Prtition Magic... it says tht ERROR 117: PARTITION'S DRIVE LETTER CANNOT BE IDENTIFIED.... and the program exits.... is there a way to bypass this error message so tht i can go ahead with partition magic.. ???????

help guys.. its urgent..