NIS - Where's the PC?

I have Norton Internet Security which covers just 1 PC (currently on my old Toshiba laptop).  I have recently bought a new HP laptop and just renewed the subscription from the free one that came with the PC.  My 'new' NIS 2011 allows me to cover 3 pc's.  My question is this - where do the PC's have to be?  I plan to give my Mum the Toshiba (she lives 250 miles from me) - can she use my '1 PC' subscription until it expires and then can I merely get her to download my 2011 version to the Toshiba as part of the 3 PC's?

 

I hope that I have made this question clear.  Thank you for your help.