This excerpt taken from the NPSP DEF 14A filed Apr 11, 2005.
Revocability of Proxies
Any stockholder giving a proxy pursuant to this solicitation has the power to revoke it at any time before it is voted. It may be revoked by filing with the Secretary of the Company, (i) at the Companys headquarters, 383 Colorow Drive, Salt Lake City, Utah 84108 until 5:00 p.m. on May 11, 2005, or (ii) in care of Hilton Parsippany, One Hilton Court, Parsippany, NJ between 9:00 a.m. and 3:00 p.m. EST on May 12, 2005, a written notice of revocation or a duly executed proxy bearing a later date, or it may be revoked by attending the Annual Meeting and voting in person. Attendance at the Annual Meeting will not, by itself, revoke a proxy.