* Wall Street coming off worst week of 2013
* Halliburton rallies in premarket after results
* Power-One soars after $1 billion purchase offer from ABB
* Futures up: Dow 33 pts, S&P 4.4 pts, Nasdaq 10.75 pts
By Chuck Mikolajczak
NEW YORK, April 22 (Reuters) - U.S. stocks were set for a modestly higher open on Monday, rebounding from stocks' worst week in 2013, as earnings from Caterpillar, Halliburton and other major companies pointed to choppy trading ahead.
Wall Street is coming off a week of extreme volatility, with the CBOE Volatility index jumping 24 percent, the biggest weekly gain for the so-called fear index this year.
The swings were largely driven by weak corporate earnings and signs of slowing growth from China, which contributed to a precipitous drop in commodity prices. The week's decline fueled talk that the market's long-awaited pullback had arrived, though the S&P remains up 9 percent on the year.
However, equities rose on Friday, and the follow-through by Monday's futures suggested that investors may still use market weakness as a buying opportunity.
Caterpillar reported results early Monday, and shares advanced 0.6 percent to $80.88 in premarket trading. Halliburton rose 3.9 percent to $38.66 before the opening bell after posting its results.
"This is all going to be very much a direction driven by earnings," said Peter Kenny, managing director at Knight Capital in Jersey City, New Jersey.
"The majors are only off 3 to 4 percent from the high but we have done that fairly efficiently and if earnings are any indication, there is going to be more choppy action ahead."
Earnings also due on Monday included Texas Instruments and Netflix Inc after the market's close. For the week, 168 companies in the S&P 500 are scheduled to report earnings.
With 104 S&P 500 components having reported through Friday, 67.3 percent of companies have topped profit expectations, according to Thomson Reuters data. Analysts expect earnings growth of 2.1 percent this quarter, up from expectations of 1.5 percent at the start of the month.
S&P 500 futures rose 4.4 points and were above 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 added 33 points and Nasdaq 100 futures gained 10.75 points.
Investors will be looking to the S&P 500's 50-day moving average of 1,543.9, which could serve as a level of market support. The index closed under that level for the first time this year on Thursday but rebounded above it on Friday.
Economic data due on Monday includes March existing-home sales at 10 a.m. (1400 GMT). Economists in a Reuters survey forecast 5.01 million units at an annualized rate compared with 4.98 million in February.
Power-One Inc soared 55.9 percent to $6.30 in premarket trading after ABB agreed to buy the company for about $1 billion.
U.S. stocks mostly rose on Friday, boosted by strong results from Google Inc and Microsoft Corp. However, the Dow was severely pressured by weakness in IBM, McDonald's and General Electric Co, all of which reported earnings that disappointed investors.