Windows Ultimate 64-bit

I am unable to create a system recovery disk for my studio 1558. I has has been partitioned and therefore not as it was when it left the factory and apparently this is the reason the repair disk facilty is not available to me. Could someone please advise me the best way around this? I assume I need to back up my C:\ drive to an external hard drive? or do I need to back it up to disk? I am not techie minded and any pointers (in non-techie-speak) would be most welcome.

Thank you