Filed pursuant to Rule 424(b)(3)

REGISTRATION NO. 333-132286

SUPPLEMENT NO. 4

(To Prospectus Supplement Dated November 9, 2006

To Prospectus Dated March 8, 2006)

$2,500,000,000 0.125% Convertible Senior Notes due 2011

$2,500,000,000 0.375% Convertible Senior Notes due 2013

This supplement no. 4 supplements our prospectus supplement dated November 9, 2006 to our prospectus dated March 8, 2006 relating to the resale from time to time by certain selling security holders of up to $2,500,000,000 principal amount of 0.125% Convertible Senior Notes due 2011 (the “2011 notes”) and $2,500,000,000 principal amount of 0.375% Convertible Senior Notes due 2013 (the “2013 notes” and, together with the 2011 notes, the “notes”) and the shares of common stock issuable upon conversion of the notes. You should read this supplement no. 4 in conjunction with the prospectus supplement and the prospectus. This supplement no. 4 is qualified by reference to the prospectus supplement and the prospectus, except to the extent that the information in this supplement no. 4 supersedes that information.

The information appearing under the heading “Selling Security Holders” in the prospectus supplement is hereby amended by the addition or substitution, as applicable, of the following:

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To the extent that any of the selling security holders identified above are broker-dealers, they may be deemed to be, under interpretations of the SEC, “underwriters” within the meaning of the Securities Act.

With respect to selling security holders that are affiliates of broker-dealers, based on information provided by the selling security holders, we believe that such entities acquired their notes or shares of common stock issuable upon conversion of the notes in the ordinary course of business and, at the time of the purchase of the notes or shares of common stock issuable upon conversion of the notes, such selling security holders had no agreements, understandings or arrangements, directly or indirectly, with any person to distribute the notes or shares of common stock issuable upon conversion of the notes.

Based upon information provided by the selling security holders, none of the selling security holders nor any of their affiliates, officers, directors or principal equity holders has held any position or office or has had any material relationship with us within the past three years. None of the selling security holders listed above owned 1% or more of our outstanding common stock either before or after this offering.

Information concerning the selling security holders may change from time to time and any changed information will be set forth in additional supplements to the prospectus supplement if and when necessary. In addition, the conversion rate and, therefore, the number of shares of common stock issuable upon conversion of the notes, is subject to adjustment under certain circumstances.

See “RISK FACTORS” beginning on page S-4 of the prospectus supplement for information you should consider before buying any securities hereunder.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this supplement, the prospectus supplement or the prospectus. Any representation to the contrary is a criminal offense.

The date of this supplement is November 16, 2007.