FAIRFAX, Va. (AP) - The Pentagon is conducting what is believed to be the largest-ever simultaneous test of computer systems to make sure Year 2000 problems won't prevent delivery of everything from bullets to toilet paper to American troops. With only one day remaining in the week-long test, the Pentagon said Tuesday it had identified and fixed three minor glitches in its enormously complex computerized logistics network. Technical experts built a duplicate network, called a "parallel processing environment," then rolled those computer clocks forward to simulate the week following Feb. 28, 2000. The Defense Department needs to watch how its systems behaved during the date rollover from 1999 to 2000, and it needs to make sure computers will recognize the next leap year.