* Govt shutdown enters second day with no end in sight
* ADP report may hold extra weight, as some data delayed
* Top Microsoft investors urge Gates to step down
* Futures down: Dow 100 pts, S&P 12.1 pts, Nasdaq 17 pts
By Ryan Vlastelica
NEW YORK, Oct 2 (Reuters) - U.S. stock index futures fell on Wednesday as a partial government shutdown in Washington entered a second day, adding to concerns about when the issue might be resolved.
* There were few signs that Congress was making progress in agreeing on a spending bill that would reopen operations. The Democratic-led U.S. Senate voted Tuesday to kill Republicans' latest attempts to modify an emergency funding bill, stripping proposed amendments from the spending bill and sending back to the House a "clean" bill that would fund government agencies until Nov. 15.
* While many investors expect the shutdown will be short-lived, its impact on economic growth and market volatility will likely be greater the longer it continues. Market participants are also watching the situation for an indication of how an impending debate on the debt ceiling might play out. That issue is considered far more important for the economy, as it could result in an unprecedented debt default if not passed.
* Sectors tied to the pace of economic growth, including financials and materials, were the most volatile amid the uncertainty. Citigroup Inc fell 1.1 percent to $48.05 in premarket trading.
* S&P 500 futures fell 12.1 points and were below fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures fell 100 points and Nasdaq 100 futures sank 17 points.
* The S&P 500 is up less than 0.2 percent over the past two sessions, a slight move that masks the volatility seen this week. Wall Street plunged on Monday as the deadline to keep the government open approached, then rebounded on Tuesday on bets the government shutdown would be short-lived.
* Wall Street has managed to avoid steep declines during similar incidents in the past. During the federal government shutdown from Dec. 15, 1995 to Jan. 6, 1996, the S&P 500 added 0.1 percent. During the Nov. 13 to Nov. 19, 1995, shutdown, the benchmark index rose 1.3 percent.
* Up to 1 million government workers remained on unpaid leave Wednesday as a result of the closure, with a fight over President Barack Obama's healthcare law at the center of the impasse. In addition, the shutdown delayed the release of government economic data, including August construction spending on Tuesday.
* If no deal is reached by Friday, the closely watched payroll report will not be released, a prospect that could put more weight on the ADP employment report, scheduled for release Wednesday at 8:15 a.m (1215 GMT). About 180,000 private sectors jobs are expected to have been added in September, up 4,000 from the previous month.
* Three of the top 20 investors in Microsoft Corp are lobbying the board to press for Bill Gates to step down as chairman of the software company he co-founded 38 years ago, according to people familiar with matter.
* A J.C. Penney Co shareholder sued the struggling retailer Tuesday over its surprise decision to issue more than $810 million of stock to shore up liquidity, which led to a steep drop in its share price in after-hours trading.
* The Empire State Realty Trust Inc, which owns the Empire State Building, said late Tuesday it had sold 71.5 million shares in an initial public offering at $13 apiece, at the low end of its expected range, to raise $929.5 million. The shares are due to begin trading Wednesday on the New York Stock Exchange.