Marilyn Helding, 65-year-old widow of a Wisconsin vegetable farmer, thought the money from her husband's estate vanished like crops in the Dust Bowl when Windsor Capital Corp. went out of business. ``I nearly went crazy when they went under,'' Mrs. Helding said from her home in Franksville, Wis. ``I didn't know what to do.'' A few months after the small Milwaukee brokerage collapsed under apparent mismanagement in March 1988, Mrs. Helding regained her entire stock portfolio and $45,000 in cash the firm owed her. The message: If your broker goes bust your investment doesn't have to. With the recent collapse of Drexel Burnham Lambert Inc., two other brokerage bankruptcy court filings in the last year and widely publicized problems at several Wall Street firms, the safety of customer accounts is drawing attention. An agency established by Congress after a rash of brokerage house failures in the late 1960s protects investors who may have thought their account went down the drain with the company that managed it. The Securities Investor Protection Corp. has a $485 million fund that insures individual accounts for up to $500,000, including up to $100,000 in cash. Large brokerages also have insurance for larger amounts. Tapping into the protection fund is a last resort. If a brokerage firm goes belly up, SIPC first tries to arrange a transfer of customer accounts to another firm. ``The basic intention is that a customer should not lose assets or property because the broker with whom (he is) doing business has encountered financial difficulty,'' said Theodore H. Focht, SIPC's president and general counsel. SIPC _ pronounced sippick _ covers all forms of stock and bond holdings but not commodities. It also does not guarantee the underlying value of a customer account. For example, if XYZ Co. is trading at $50 a share when a brokerage folds but falls to $5 at reimbursement time, the customer loses the difference. ``It does not insure you for market losses,'' said Irving Picard, a New York bankruptcy lawyer who has served as a court-appointed SIPC trustee in three liquidation cases. ``If you think the broker defrauded you ... that's not protected by the SIPC fund.'' In the 19 years since its creation, SIPC has handled 212 cases and paid $185 million to satisfy customer claims. If a firm can't immediately pay, SIPC will advance the money to customers and try to collect later. SIPC officials estimate that cash and securities worth $1.4 billion have been returned to about 240,000 investors, mostly through account transfers. A total of 305 claims worth $31 million have not been satisfied, primarily because of legal challenges. The SIPC fund, comparable to the Federal Deposit Insurance Corp. for commercial banks, is fed by required contributions from the nation's 12,000 or so registered broker-dealers. The Washington-based agency also has $500 million in bank credit and a $1 billion line to the U.S. Treasury. Neither resource has been tapped. On top of that, about 25 firms have private coverage of up to $5 million per account. Before SIPC was signed into law by President Nixon on Dec. 30, 1970, self-regulatory organizations _ the National Association of Securities Dealers and the stock exchanges _ set aside funds to protect customers of collapsed firms. But in the late 1960s, Wall Street was hit with a rash of failures when the market slumped as firms spent large sums to computerize. When its customer protection kitty dried up, the New York Stock Exchange was forced to dip into a building fund to safeguard investors. Fearing the worst, the exchanges lobbied Congress for help. There were six SIPC cases last year _ five involved a total of under 50 claims. The most cases in one year was 40 in 1972, during a recession. A rash of financial fraud was partly responsible for 46 cases from 1981-85. SIPC's largest payout, $32.5 million, involved the 1983 criminal fraud-related collapse of Bell & Beckwith of Toledo, Ohio. The demise of Fitzgerald, DeArman & Roberts Inc. of Tulsa, Okla., involved the most customer accounts, 50,000. SIPC has doled out $5.5 million since that case began in June 1988. SIPC can get involved when a broker-dealer enters bankruptcy court proceedings, when a trustee or receiver is appointed to run a firm, when a firm fails to meet federal requirements or when it can't demonstrate compliance. A brokerage can request a SIPC-run liquidation or SIPC can ask the Securities and Exchange Commission to seek a court order for one. Drexel, for example, was not placed in a SIPC proceeding because only its parent company filed for federal bankruptcy court protection and the firm is liquidating orderly. Plus, Drexel sold most retail accounts to Smith Barney, Harris Upham & Co. last year and the rest went to Shearson Lehman Hutton Inc. after the bankruptcy filing.