Trust Tax Services of America S-4 Registration of securities issued in business combination transactions

Exhibit 5.1

SIMPSON THACHER & BARTLETTLLP

425 LEXINGTON AVENUE

NEW YORK, N.Y. 10017-3954

(212) 455-2000

Facsimile (212) 455-2502

April 19, 2006

SunGard Data Systems Inc.

680 East Swedesford Road

Wayne, Pennsylvania 19087

Ladies and Gentlemen:

We have acted as counsel to SunGard Data Systems Inc., a Delaware corporation (the “Company”), and the subsidiaries of the Company listed on Schedule I hereto (collectively, the “Guarantors”), in connection with the Registration Statement on Form S-4 (the “Registration Statement”) filed by the Company and the Guarantors with the Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933, as amended, relating to (i) the issuance by the Company of $1,600,000,000 aggregate principal amount of 9 ¹/8% Senior Notes due 2013 (the “Senior Fixed Rate Exchange Notes”) and $400,000,000 aggregate principal amount of Senior Floating Rate Notes due 2013 (the “Senior Floating Rate Exchange Notes” and, together with the Senior Fixed Rate Exchange Notes, the “Senior Exchange Notes”) and the issuance by the Guarantors of guarantees (the “Senior Guarantees”) with respect to the Senior Exchange Notes and (ii) the issuance by the Company of $1,000,000,000 aggregate principal amount of 10 ¹/4% Senior Subordinated Notes due 2015 (the “Senior Subordinated Exchange Notes” and, together with the Senior Exchange Notes, the “Exchange Notes”) and the issuance by the Guarantors of guarantees (the “Senior Subordinated Guarantees” and, together with the Senior Guarantees, the “Guarantees”) with respect to the Senior Subordinated Exchange Notes. The Senior Exchange Notes and the Senior Guarantees will be issued under an indenture dated as of August 11, 2005 (the “Senior Indenture”) among the Company, Solar Capital Corp., a Delaware corporation which merged with and into the Company (“Solar”), the Guarantors and The Bank of New York, as trustee (the “Trustee”), and the Senior Subordinated Exchange Notes and the Senior Subordinated Guarantees will be issued under an indenture dated as of August 11, 2005 (the “Senior Subordinated Indenture” and, together with the Senior Indenture, the

“Indentures”) among the Company, Solar, the Guarantors and the Trustee. The Senior Fixed Rate Exchange Notes will be offered by the Company in exchange for $1,600,000,000 aggregate principal amount of its outstanding 9 ¹/8% Senior Notes due 2013, the Senior Floating Rate Exchange Notes will be offered by the Company in exchange for $400,000,000 aggregate principal amount of its outstanding Senior Floating Rate Notes 2013 and the Senior Subordinated Exchange Notes will be offered by the Company in exchange for $1,000,000,000 aggregate principal amount of its outstanding 10 ¹/4% Senior Subordinated Notes due 2015.

We have examined the Registration Statement and the Indentures, which have been filed with the Commission as exhibits to the Registration Statement. We also have examined the originals, or duplicates or certified or conformed copies, of such corporate records, agreements, documents and other instruments and have made such other investigations as we have deemed relevant and necessary in connection with the opinions hereinafter set forth.As to questions of fact material to this opinion, we have relied upon certificates or comparable documents of public officials and of officers and representatives of the Company and the Guarantors.

In rendering the opinions set forth below, we have assumed the genuineness of all signatures, the legal capacity of natural persons, the authenticity of all documents submitted to us as originals, the conformity to original documents of all documents submitted to us as duplicates or certified or conformed copies and the authenticity of the originals of such latter documents. We also have assumed that the Indentures are the valid and legally binding obligations of the Trustee.

Based upon the foregoing, and subject to the qualifications, assumptions and limitations stated herein, we are of the opinion that:

1. When the Exchange Notes have been duly executed, authenticated, issued and delivered in accordance with the provisions of the applicable Indenture upon the respective exchanges described above, the Exchange Notes will constitute valid and legally binding obligations of the Company enforceable against the Company in accordance with their terms.

2. When (a) the Exchange Notes have been duly executed, authenticated, issued and delivered in accordance with the provisions of the applicable Indenture upon the respective exchanges and (b) the Guarantees have been duly issued, the Guarantees will constitute valid and legally binding obligations of the Guarantors enforceable against the Guarantors in accordance with their terms.

2

Our opinions set forth above are subject to (i) the effects of bankruptcy, insolvency, fraudulent conveyance, reorganization, moratorium and other similar laws relating to or affecting creditors’ rights generally, (ii) general equitable principles (whether considered in a proceeding in equity or at law) and (iii) an implied covenant of good faith and fair dealing.

Insofar as the opinions expressed herein relate to or are dependent upon matters governed by (i) the laws of the State of California, (ii) the laws of the States of Florida or Pennsylvania, (iii) the laws of the State of Massachusetts or (iv) the laws of the State of Utah, we have relied upon (a) the opinion of Sheppard, Mullin, Richter & Hampton LLP, dated the date hereof, (b) the opinion of Blank Rome LLP, dated the date hereof, (c) the opinion of Ropes & Gray LLP, dated the date hereof and (d) the opinion of Snell & Wilmer L.L.P., dated the date hereof, respectively.

We do not express any opinion herein concerning any law other than the law of the State of New York, the federal law of the United States, the Delaware General Corporation Law (including the statutory provisions, all applicable provisions of the Delaware Constitution and reported judicial decisions interpreting the foregoing), the Delaware Limited Liability Company Law and, to the extent set forth herein, the laws of the States of California, Florida, Pennsylvania, Massachusetts and Utah.

We hereby consent to the filing of this opinion letter as Exhibit 5.1 to the Registration Statement and to the use of our name under the caption “Legal Matters” in the Prospectus included in the Registration Statement.

Very truly yours,

/s/ Simpson Thacher & Bartlett LLP

SIMPSON THACHER & BARTLETT LLP

Schedule I

ASC Software Inc.

Assent Software LLC

Automated Securities Clearance LLC

BancWare LLC

Data Technology Services Inc.

Derivatech Risk Solutions Inc.

Exeter Educational Management Systems, Inc.

FDP LLC

Financial Data Planning Corp.

HTE-UCS, Inc.

Inflow LLC

MBM Inc.

MicroHedge LLC

Online Securities Processing Inc.

Plaid Brothers Software, Inc.

Portfolio Ventures Inc.

Prescient Markets Inc.

SIS Europe Holdings Inc.

SRS Development Inc.

SunGard Advisor Technologies Inc.

SunGard Asia Pacific Inc.

SunGard Asset Management Systems LLC

SunGard Availability Services LP

SunGard Availability Services Ltd.

SunGard Bi-Tech LLC

SunGard BSR Inc.

SunGard Business Systems LLC

SunGard Canada Holdings Inc.

SunGard Collegis Inc.

SunGard Computer Services LLC

SunGard Consulting Services Inc.

SunGard Corbel LLC

SunGard CSA LLC

SunGard Data Systems Inc.

SunGard Development Corporation

SunGard DIS Inc.

SunGard Energy Systems Inc.

SunGard eProcess Intelligence Inc.

SunGard ERisk Inc.

SunGard Expert Solutions Inc.

SunGard Financial Systems LLC

SunGard HTE Inc.

SunGard Insurance Systems LLC

SunGard Investment Products Inc.

SunGard Investment Systems LLC

SunGard Investment Ventures LLC

SunGard Kiodex Inc.

SunGard NetWork Solutions Inc.

SunGard Pentamation Inc.

SunGard Reference Data Solutions Inc.

SunGard SAS Holdings Inc.

SunGard SCT Inc.

SunGard Securities Finance LLC

SunGard Securities Finance International Inc.

SunGard Shareholder Systems LLC

SunGard Software, Inc.

SunGard Systems International Inc.

SunGard Technology Services LLC

SunGard Trading Systems VAR LLC

SunGard Treasury Systems Inc.

SunGard Trust Systems LLC

SunGard Workflow Solutions LLC

Systems & Computer Technology Corporation

The GetPaid LLC

Trust Tax Services of America, Inc.

Wall Street Concepts Inc.

World Systems Inc.