IBM executive, Garry Norris, provides most detailed allegations yet to arise in Microsoft antitrust trial of how Microsoft wielded its market power to put pressure on personal computer makers to favor Microsoft's software; Norris describes Microsoft's 'take-it-or-leave-it' arrogance when he objected to company's prices and terms for its industry-standard Windows operating system; Norris handled relations between IBM PC business and Microsoft from 1995 to 1997; Norris's testimony is backed up by new documents entered into evidence, including internal IBM memos as well as letters and E-mail between two companies; Microsoft says Norris is exaggerating what were complex negotiations, but unless Norris's testimony is refuted in cross-examination, his testimony appears to lend new ammunition to Government's case against Microsoft; photo (M)