Partitioning a HD

Hi Guys;
this is my first time in a forum, so excuse any mistakes I make. I tried partitioning a HD for back up data purposes,on my HP Pavilion 540n,with the OS already installed (I'm running XP Home) and I followed the instructions on the tutorial,I got to Disk Management,click on it,I see 2 partitions: 1) HP RECOVERY(4.30GB) 2) HP-PAVILION C: (32.70GB) I right click on the C: partition because that's the one I'm supposed to partition but the only options I get are OPEN,EXPLORE,CHANGE DRIVE LETTERS AND PATHS, PROPERTIES AND HELP while FORMAT,MARK PARTITION AS ACTIVE AND DELETE PARTITION show as inactive, so I don't know where to go from there, I thought it was because I am supposed to reinstall the OS, but I tried that an my laptop using the restored CDs and it wouldn't give me the option to enter any values for a partition or ask if I wanted to create any logical drives, it automatically did it all. can somebody help me understand why or what is it that I am doing wrong? Thank you.