(Check One): ¨  Form 10-K ¨  Form 20-F ¨  Form 11-K     x  Form 10-Q ¨  Form N-SAR ¨  Form N-CSR	UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 FORM 12b-25 NOTIFICATION OF LATE FILING
		SEC FILE NUMBER 000-26937
		CUSIP NUMBER 74834 T 10 3

For Period Ended: September 30, 2006

¨  Transition Report on Form 10-K

¨  Transition Report on Form 20-F

¨  Transition Report on Form 11-K

¨  Transition Report on Form 10-Q

¨  Transition Report on Form N-SAR

For the Transition Period Ended:                                                              

Read Instruction (on back page) Before Preparing Form. Please Print or Type.

Nothing in this form shall be construed to imply that the Commission has verified any information contained herein.

If the notification relates to a portion of the filing checked above, identify the Item(s) to which the notification relates:

PART I — REGISTRANT INFORMATION

Quest Software, Inc.

(Full Name of Registrant)

N/A

(Former Name if Applicable)

5 Polaris Way

(Address of Principal Executive Office (Street and Number))

Aliso Viejo, California 92656

(City, State and Zip Code)

PART II — RULES 12b-25(b) AND (c)

If the subject report could not be filed without unreasonable effort or expense and the registrant seeks relief pursuant to Rule 12b-25(b), the following should be completed. (Check box if appropriate)

(a)	The reasons described in reasonable detail in Part III of this form could not be eliminated without unreasonable effort or expense;
(b)	The subject annual report, semi-annual report, transition report on Form 10-K, Form 20-F,11-K Form N-SAR or Form N-CSR, or portion thereof, will be filed on or before the fifteenth calendar day following the prescribed due date; or the subject quarterly report or transition report on Form 10-Q, or portion thereof, will be filed on or before the fifth calendar day following the prescribed due date; and
(c)	The accountant’s statement or other exhibit required by Rule 12b-25(c) has been attached if applicable.

PART III — NARRATIVE

State below in reasonable detail the reasons why Forms 10-K, 20-F, 11-K, 10-Q, N-SAR, or the transition report portion thereof, could not be filed within the prescribed time period.

As previously announced, the board of directors of Quest Software, Inc. (“Quest”) established a special committee of independent directors to review Quest’s historical stock option grant practices and related accounting. Although the special committee has not completed its work or reached final conclusions and is continuing its investigation, its preliminary conclusions are that (i) accounting measurement dates for many of Quest’s stock option grants were incorrectly determined for financial reporting purposes, (ii) non-cash stock-based compensation expense should have been recorded with respect to those stock option grants and recognized over the vesting period of the options, and (iii) the amount of such additional expense is expected to be material.

Accordingly, Quest has determined that it will have to restate its annual financial statements for the periods from 2000 through 2005 and its financial statements for the quarter ended March 31, 2006. The Company intends to file its quarterly reports on Form 10-Q for the quarters ended September 30, 2006 and June 30, 2006 and amend its previously filed annual report on Form 10-K, as amended, for the year ended December 31, 2005 and quarterly report on Form 10-Q for the quarter ended March 31, 2006 as soon as practicable after the completion of the special committee’s investigation.

PART IV — OTHER INFORMATION

(1) Name and telephone number of person to contact in regard to this notification

J. Michael Vaughn (Name)     (949)     (Area Code) 754-8000 (Telephone Number)

(2) Have all other periodic reports required under Section 13 or 15(d) of the Securities Exchange Act of 1934 or Section 30 of the Investment Company Act of 1940 during the preceding 12 months or for such shorter period that the registrant was required to file such report(s) been filed? If answer is no, identify report(s).    ¨  Yes    x  No

The registrant has not yet filed its quarterly report on Form 10-Q for the quarter ended June 30, 2006.

(3) Is it anticipated that any significant change in results of operations from the corresponding period for the last fiscal year will be reflected by the earnings statements to be included in the subject report or portion thereof?    ¨  Yes    ¨  No *

If so, attach an explanation of the anticipated change, both narratively and quantitatively, and, if appropriate, state the reasons why a reasonable estimate of the results cannot be made.

* The registrant has not checked either box in Part IV, item (3). The registrant has previously reported its determination that it will restate its historical financial statements, including its financial statements for the quarterly period ended September 30, 2005. Due to the pending Special Committee investigation described in Part III of this Notification, the registrant has not yet determined the amounts of additional non-cash, stock-based compensation expense to be recorded for the periods in question or, for periods following 2005, the adjustments to the registrant’s calculations of the fair value of share-based payments using new accounting measurement dates. Accordingly, the registrant cannot yet estimate the extent and timing of the various adjustments to its prior financial statements that will be required as a result of the investigation and, thus cannot yet determine whether any significant change will be reflected in its results of operations for the period ended September 30, 2006 compared to its results of operations from the corresponding period of the prior year.

Quest Software, Inc.

(Name of Registrant as Specified in Charter)

Has caused this notification to be signed on its behalf by the undersigned hereunto duly authorized.

Date November 9, 2006	By	/s/ Michael J. Lambert
		Senior Vice President, Chief Financial Officer

INSTRUCTION: The form may be signed by an executive officer of the registrant or by any other duly authorized representative. The name and title of the person signing the form shall be typed or printed beneath the signature. If the statement is signed on behalf of the registrant by an authorized representative (other than an executive officer), evidence of the representative’s authority to sign on behalf of the registrant shall be filed with the form.

ATTENTION

Intentional misstatements or omissions of fact constitute Federal Criminal Violations (See 18 U.S.C. 1001).

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