Hurricane Katrina has sent a number of stock groups rising, from oil and natural gas producers to cement companies. One company that's also up is troubled UnitedRentals (NYSE:URI).

United Rentals is the largest equipment rental company in the U.S. It offers more than 600 types of equipment for rent, from construction equipment, industrial and heavy machinery, and traffic equipment to items for homeowners. With all the Katrina-related rebuilding expected, United Rentals is certainly well-positioned to help.

Investors, though, are not in a position to do much of an evaluation. The company has not reported complete results since October 2004. The latest SEC filing, which provides only preliminary results for the quarter ended June 30, shows same-store rental revenue up a strong 11.4%. United Rentals also gave 2005 earnings guidance of $1.60 to $1.70 a share, and projected free cash flow of $200 million. Sounds good, right?

The company has been unable to report complete results because it is going to restate periods before 2004. An SEC investigation into its accounting practices has also been gumming up the works.

United Rentals is also having trouble resolving debt problems. It posted $3.14 billion in total debt (as of 2004, of course) and negative 2.1 times interest coverage. (For the latest year data is available, interest expense is two times the company's operating loss.) Debt is a big concern, even when you can show that your business benefits from hurricanes.

The stock was off to a rapid start this morning, up $1.09 (5.5%), but that move was nipped in the bud when Moody's (NYSE:MCO) lowered the company's debt rating and said it may downgrade it again. Business may become good, but in my opinion, the debt monster needs to be fed before the stock really takes off.

For the time being, investors may want to focus on Motley Fool Inside Value recommendation Home Depot (NYSE:HD) and its growing rental business. It's a lot safer to play in the value pool than to venture into United Rentals' muddy waters.

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Fool contributor W.D. Crotty owns shares in Home Depot. Click here to see The Motley Fool's disclosure policy.