Advanced Accounting 5.1 runs under all operating systems released to date by Microsoft including XP and 2000. They are different configuration issues (that are in general not specific to Advanced Accounting) in each different operating system however. See the technical issues section and the latest technical support memos for pertinent information.
NOTE: business users should always choose XP Professional and NOT use XP Home for reasons unrelated to Advanced Accounting. See our technical support memo area (linked to above) for further information.