[xubuntu-users] Unable to upgrade xubunto

[Joshua]

Trying to upgrade my PC from 13.04 to the latest supported xubunto version.

When clicking "Install Now" in Software Updater the following message 
appears:

      "The upgrade needs a total of 41.7 M free space on disk '/boot'. 
Please free at least an additional 41.7 M of disk space on '/boot'. 
Empty your trash and remove temporary packages of former installations 
using 'sudo apt-get clean'."

However, my PC does has enough space (and, in addition, 'sudo apt-get 
clean' does not seem to do anything either).

Can someone offer some advice as to what to do?

  Thanks,

Josh