Hello JanOtterson,
The support for Windows 98 has ended.
For reference:
http://support.microsoft.com/ph/1139
For Windows 98 compatibility, you'll need to check the specifications on the hardware and software that ships with it. Windows 98 does not support wireless zero configuration, so there will have to be some type of control software installed, in order to set up the wireless adapter.
Please check the links below to check the features and compatibality for Windows 7 as it is the latest one and supports wireless connectivity.
http://windows.microsoft.com/en-US/windows7/products/features
For Windows 7 system requirement:
http://windows.microsoft.com/en-US/windows7/products/system-requirements
Windows 7 Upgrade Advisor:
http://www.microsoft.com/download/en/details.aspx?id=20
To purchase Windows 7 please click on the link below:
http://www.microsoft.com/windows/buy/default.aspx
Hope the information helps.
Regards.