Norton AntiVirus 2009...subscription ending???

I purchased a new computer back in April and had Norton Antivirus 2009 with Antispyware installed at the store.  In the last little while,  I have been getting a message saying my subscription will be ending,  Oct 24 to be exact.  It says one year protection on the product so why am I being told to renew after only 6 months???  Any help would be greatly appreciated,  thanks.