Lead from the front Texas Nodal 1 EDS 3 Release 5 Phase 1 Testing Monday / Friday Market Updates August 27, 2007

Lead from the front Texas Nodal 2 Agenda Antitrust Admonition Roll Call Review of Testing Schedule –Week’s Plans (Monday) –Week’s Accomplishments (Friday) Lessons Learned (common MP Issues, questions, etc) Issues Management (Know Issues Log) –Existing Known Issues (ERCOT Systems) –New Issues Description and Status Q&A / Open Forum

Lead from the front Texas Nodal 3 Antitrust Admonition ANTITRUST ADMONITION ERCOT strictly prohibits Market Participants and their employees who are participating in ERCOT activities from using their participation in ERCOT activities as a forum for engaging in practices or communications that violate the antitrust laws. The ERCOT Board has approved guidelines for members of ERCOT Committees, Subcommittees and Working Groups to be reviewed and followed by each Market Participant attending ERCOT meetings. If you have not received a copy of these Guidelines, copies are available at the Client Relations desk. Please remember your ongoing obligation to comply with all applicable laws, including the antitrust laws.

Lead from the front Texas Nodal 4 Review of Testing Schedule : Week’s Plans Tests Scheduled for this week 8/27 –“PING” Test TXU 8/30 BTU 8/31 –Support / Testing Call CPS City of San Antonio 8/28 Reliant 8/28 Tests Scheduled for week beginning 9/03 –“PING” Test Coral 9/7 NRG 9/7 Suez 9/7 –Support / Testing Call LCRA 9/4 BTU 9/5 TXU 9/5 Review Known Issues in Progress (See Known Issues Slide)

Lead from the front Texas Nodal 5 Lessons Learned (common MP Issues, questions, etc) –“PING” Test Have the right people and resources ready for the test and aware of their role –Workstation Administrator –Network Administrator –QSE EDS PM –Application SME Available access to production systems Plan for the full hour in case issues arise Wait for digital certificate to download browser plug-in for MMS UI (notify if issues arise) – Access MMS UI w/ certificate to get correct version of Determine in advance if your cyber security / network group will allow telnet / ping from the datacenter to internet address. –Support / Testing Call Send sample transactions (Create COP, TPO and OS) at least 1 ½ weeks prior to test –Make sample transactions small (1 resource, max of three time blocks in trade date) –Base transactions on samples provided on testing package Prepare test scenarios in advance of tests

Lead from the front Texas Nodal 6 Q&A Q&A / Open Forum