How to delete new kernel & to go back in old one?

You should try searching around and finding out if there is a kernel that is known to work with your Wireless Card. If not, you can always use your older kernel one of two ways:

  1. Boot into older kernel. Depending on how your kernel was installed, you might be able to boot into your old one by holding down Shift as the computer boots, bringing up the Grub Boot menu. On this menu, there might be an option entitled "Previous Linux Versions" and inside that menu, you might find your 3.2.0-24 kernel as an option. If not, read on...
  2. Find a new kernel. If you can find a kernel that is confirmed working or even just a newer one to try out, you can try installing it from a downloaded DEB file. These can be found at the Ubuntu Packages Repository. The procedure for installing a kernel from downloaded DEB is well explained here

Hope that helps...