If it's OEM it will be tied to the motherboard of the first system it was installed in. If it's full retail is there a number to call? If so you can get a new activation number that way.
Also Windows 7 was released to retail at the end of 2009 so you have not had it over 4 years
Edit: I should learn to read before I post lol. God knows I bitch at other people enough about it. 4745454b beat me to it.