Windows Vista Can I partition C: drive after Vista is installed

I know how to partition a drive before Windows in installed but can it be done after Vista has been installed (without affecting what is already insatlled on that disk)?
I have just bought a new laptop which came with Vista already installed (C: drive). I would like to create a partition to store video (avi) files captured from my video camera so tbat I can easily format just the new partition as capturing is best done to a drive which is not fragmented plus even the empty space on a drive which has been defragmented is not always contiguous.

 

It can be done, but BACKUP before doing anything.

Vista/Win7 have built in Disk Manager which can do the job for you.

How to Shrink and Extend NTFS Volumes in Windows Vista.

 

Thanks for the link.
I have nothing to backup as the only data on the drive is the operating system (and I have recovery disks if that is lost).

I have read the info at that link and it states that it is only possible to do this from an administrator account. I don't think that I have as when Windows boots up it displays a user logon screen which has my name but no one named ADMINISTRATOR. I have used Control Panel>User Accounts but cannot change my personal account from Limited to Administrator.

I have found this post http://www.windowsbbs.com/windows-vista/86682-windows-vista-login-administrator.html which seems to answer my question.
If it doesn't would someone please advise.
Thanks