* Major indexes on track for second week of gains
* Amazon shares fall after results; Visa, Ford also down
* Microsoft rises as earnings beat expectations
* Investors concerned over fallout to Ukraine violence
* Futures down: Dow 51 pts, S&P 6.2 pts, Nasdaq 13.75 pts (Updates prices)
NEW YORK, April 25 U.S. stock index futures pointed to a lower open on Friday as a number of bellwether names, including Amazon and Ford, fell following their quarterly results, overshadowing positive numbers from Microsoft.
* Investors also continued to pay attention to intensifying geopolitical strife after Ukrainian forces killed up to five pro-Moscow rebels and Russia launched army drills near the border. The actions raised fears Russian troops would invade. Separately, local police said seven people were injured overnight at a pro-Ukrainian checkpoint near the Black Sea port of Odessa when an explosive device blew up.
* While the situation has taken a backseat to corporate earnings in recent weeks, investors remain on edge over what the potential fallout could be to any prolonged tension or violence. Visa Inc late Thursday said U.S. sanctions on Russia were hurting its card transaction volumes and that revenue growth would slow further this quarter, sending shares down 3.7 percent to $200.50 in premarket trading.
* Amazon fell 5 percent to $320 after posting a jump in revenue, offset by sharp increases in spending. Ford Motor Co fell 2.1 percent to $15.98 in premarket trading after first-quarter earnings missed expectations, hurt by higher warranty costs in North America.
On the upside, Microsoft Corp's earnings topped analyst forecasts, while investors were cheered by the software giant's new emphasis on mobile and cloud computing. Shares rose 1.5 percent to $40.46.
* S&P 500 futures fell 6.2 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 51 points and Nasdaq 100 futures fell 13.75 points.
* For the week, the Dow is up 0.6 percent, the S&P is up 0.7 percent and the Nasdaq is up 1.3 percent. It is the second straight week of gains for all three, boosted by strong results, especially from high-profile names like Apple Inc and Caterpillar Inc.
* While companies are clearing a lowered bar, estimates have been improving. Profits are now seen rising 2.9 percent this quarter, down from the 6.5 percent growth rate estimated at the start of the year, but above the low of 0.6 percent seen last week, according to Thomson Reuters data.
* Whirlpool Corp reported adjusted earnings that rose from the prior year, and revenue that was up 4.7 percent.
* According to sources familiar with the matter, Allergan Inc approached Shire Plc in recent months about a possible takeover but was rebuffed, in the latest example of a U.S. drugmaker seeking to buy an overseas rival to lower its tax rate. (Editing by Chizu Nomiyama and Nick Zieminski)