I would never agree to buy anything like that over the phone, it could be anyone, most ISP's don't call you....you usually have to call them for help or with questions.

They may send something in the mail , but a phone call- not normal - unless you requested them to call you first...

once you activate a legal copy of windows it never expires.

I bought my XP Home ages ago & still am using it, no problems/no expiration time.

If you give the name of the program that you bought , we can look it up to see if legit & safe or not.
If it seems dicey & Norton keeps finding stuff, I'd would suggest uninstalling it and trying to cancel the money if it was a credit card purchase.

There are many Free & safe programs to be found like these on download.cnet.com -
Maintenance & Optimization -
http://download.cnet.com/windows/mai...%7C&tag=narrow