ACCPAC Simply Accounting ($199) is available for Macintosh (requires 1MB memory and an 800k disk drive), and IBM-compatible PCs (requires a minimum of 2 disk drives, 384k RAM, and DOS 3.0). The program is also compatible with Windows 3.0 or higher. To find a distributor, call 800/255-5224. An NAHB survey shows that over 75% of contractors use computers. What that number doesn't tell us, however, is how effectively they use computers. If the number of phone calls I receive from unhappy contractors is any indicator, plenty of builders feel they could be getting a lot more from their computers and software than they are getting now. Too many contractors have bought integrated construction software and have never used it. Others are no longer using it or