Microsoft had been conducting the testing using two separate beta groups: one to test the version ultimately sent to PC makers, and one testing the retail version.
But the company sent an email to the Service Pack group earlier this week informing them they would be transferred to the OEM Service Release group.
At the same time, Microsoft released an interim build of the Windows 98 OSR beta to testers, build number 2136, according to Nate Mook of the Beta News beta testing Web site.
Microsoft could not be reached for comment.
The service pack for Windows 98 will include the latest service releases for Internet Explorer, support for Modular Device Bay hardware, additional support for modem drivers, increased support for USB connections, all security updates, and networking enhancements.
The Windows 98 service pack will contain all bug fixes and security patches affecting the operating system, as well as a new feature called Internet Connection Sharing, or ICS, according to Mook.