Wubi can only support a single installation instance at a time, and although it's possible to get around this Ubuntu Studio isn't supported by Wubi until 13.04. This means you cannot install Ubuntu Studio 12.04 or 12.10 with Wubi. There are some workarounds to do this (not recommended). If you use the 13.04 Wubi then you'll be installing a development release that is in beta and not recommended for normal users. It's also not totally clear when or if Wubi 13.04 will be released.
So in order to install Ubuntu Studio you would need to install as a normal dual boot. You would do this by booting from your Ubuntu Studio DVD and select to install it. You can create some free space beforehand by splitting or deleting an existing partition, or see whether the installer can do this for you satisfactorily.
You could also update your existing Ubuntu install to Ubuntu Studio.
Note: if you reinstall with Wubi, it will delete and completely remove any old Wubi install. If you install a normal dual boot, it won't see the Wubi install or interfere with it, but you'll only be able to boot the Wubi install from Windows' boot manager (unless you manually create Grub entries for it).