For Irma Mendoza, a 34-year-old office manager in Round Rock, Tex., bank failures are nothing to lose sleep over. She's survived three of them and now bestows great confidence in the way the federal deposit insurance system works.

"Bank failures are more an inconvenience than a worry," she said, involving things like switching accounts to another institution, ordering new checks and suffering through occasional delays.

Unfortunately, regulators said, thousands of bank customers in the Northeast don't share Mendoza's calm. Unused to bank failures and nervous about losing their life savings, many have begun to question the safety of their deposits, largely because of misconceptions about the deposit insurance system and about the types of accounts that are protected.

"I just couldn't rest easy at night," Anita Freedman said of her decision to pull $50,000 in certificates of deposit out of Maryland National Bank recently. "I knew in my head that I was protected, but my nerves kept telling me to do something."

Anxieties have been heightened by the recent credit union crisis in Rhode Island, by the failure of the Bank of New England in Boston and locally by stories about troubles at Maryland National's parent company, MNC Financial Inc.

In general, banking and government officials said, the worries are groundless, so long as the financial institution's funds are federally insured. Congress, anxious to preserve confidence in the nation's financial system, is not about to let anyone lose a penny of federally protected money.

In an emergency, Congress would certainly permit the FDIC to tap Treasury funds directly to repay depositors, so in that sense, taxpayers, not depositors, are ultimately at risk.

But that doesn't mean depositors can abdicate responsibility for watching over their own savings. The trick is knowing how much of their money is covered by the $100,000 federal deposit limit -- and how much is not -- should a bank fail.

Consumers should bear in mind that, whenever possible, the government tries to sell troubled institutions to new owners rather than close them down and pay off depositors.

In these cases, even uninsured accounts of more than $100,000 are reimbursed, usually without delay. The bigger the bank the more likely it will be sold rather than closed; the federal government handles about 85 percent of all banks and thrift failures by selling the troubled institution to a new owner. But, there is no guarantee government regulators will continue this practice. With that caveat in mind, depositors should place money in federally insured banks and thrifts as though the institution may actually have to be closed and they will be reimbursed only for funds backed by insurance.

In the 15 percent of cases where an institution is closed for good, depositors in the last 10 years have been paid off in less than five days, including Saturday and Sunday. Regulators said the lag is necessary only to give them time to sort out accounts and prepare checks for customers.

Here are some basic guidelines on how deposit insurance works and what is covered:

Individual accounts: In general, depositors are insured up to a $100,000 total for all individual accounts they have in a bank or thrift.

For example, regulators consider that a person with $60,000 in a certificate of deposit, $50,000 in another CD, $5,000 in a NOW account and $900 in checking has a total of $115,900 at the bank. Of that, the government will repay $100,000 if the bank is shut down, leaving the depositor holding $15,900 in uninsured funds that, if the government chooses, the depositor could lose.

But the same depositor would be reimbursed up to an additional $100,000 for an individual retirement account or Keogh account because those are insured separately from savings and checking accounts.

If a depositor has money in two institutions that are merged, and his or her combined funds in the new institution exceed the $100,000 limit, then in general, those funds will be insured separately -- and above the $100,000 limit -- for six months after the merger.

After that time, the portion that exceeds the $100,000 ceiling will become uninsured. There are some exceptions, however, that could extend the period for which funds in excess of the ceiling are covered. Depositors should get an explanation in writing of how their funds would be affected by a merger.

If an institution is taken over and run by the government before it is closed or sold, customers may get a letter giving them notice that they have uninsured deposits in that institution. But regulators said depositors cannot count on such a letter, and so should do their own calculations of their possible exposure.

Joint accounts: In addition to coverage of $100,000 for individual accounts, a depositor is insured for up to $100,000 in joint accounts.

For example, an individual has her own account worth $100,000 and also has a joint account with her husband for $100,000, another with her daughter for $100,000 and another with her son for $100,000.

If the bank fails, she will be fully protected for the individual account, and up to $100,000 for half of the combined total of the three joint accounts. In this case, she will be covered for $100,000 of the $150,000 that represents her half of the $300,000 in joint accounts.

Trusts and other accounts: Money invested on your behalf in stock, bonds or other securities is like jewelry being kept in a safe deposit box. The Federal Deposit Insurance Corp. does not insure the value of the goods, but, upon proof of ownership, will return them to you.

Regulators caution that in any instance where a bank or thrift has even the slightest discretion on how to invest your money -- from a trust fund to the right to roll over a CD -- consumers should be sure to read contracts carefully before signing and to keep detailed records.

Written evidence of ownership will go a long way to helping convince regulators of your claims, though officials caution that, in a dispute, they must determine whether money is insured on a case-by-case basis.

Credit unions: These institutions are insured under a separate system from banks and thrifts, but generally the rules for coverage follow those governing FDIC-insured institutions. The 415 credit unions in Virginia and the District carry federal insurance.

In Maryland, however, which has 167 federally insured credit unions, there are also 13 credit unions insured privately by the Credit Union Insurance Corp. The CUIC is funded by the 13 credit unions and provides insurance up to $100,000 under rules similar to those covering federally insured institutions.

Although the 13 credit unions are regulated by the state, depositors should be aware that private deposit insurance doesn't carry the degree of certainty that federal protection does.

If a privately insured credit union should fail and the CUIC didn't have enough money to repay depositors, neither the federal government nor the state of Maryland would be obligated to step in.