My inspiron 1545 keyboard layout has the same "problem" : no numkey,no additional numpad.
As a workaround one can use:
>the "character map" => click START button,type charmap,press ENTER and choose from the table
>download "autohotkey.exe" - install it
after installing right click on the desktop - choose "New" from the menu and create a new "Autohotkey script"
Right click the new (almost)empty script choose EDIT script and add the following lines at the very end.
save the file,double click the file and try it........
Note:While the script is running you don't have access to the signs above the standard numbers => !,",£,$%^&*()
If you need them again just exit the script.....you may use autohotkey to create a better script than mine-it's just an idea.