I haven’t taken a journey down this relic lane for a while but here is what I recall of the progression. While there is no update to transform ’98 into “98 SE,” by using the windows update site and maybe some poking at another ms site (listed below), you can make the products somewhere between 98% and 100% identical.
First here are some discussion about the difference between the two. I liked the 2nd article.
http://kb.iu.edu/data/agli.html
http://thetechnozone.com/pcbuyersguide/software/system/Win98SE.html
here is a detailed discussion of ’98 SE regarding the updated components.
http://support.microsoft.com/?kbid=234762
next this site lists most of the updates, hot fixes, security patches, added capabilities.
http://www.microsoft.com/windows98/downloads/corporate.asp
lastly, go to windowsupdate.microsoft.com
The drill is to run through the windows updates until it doesn’t offer any more. Then try the devices you want. If it still doesn’t work, go to the site above for additional updates/hot fixes and so forth.
Note that not everything that manufacturers say will run with ’98 will actually run with ‘98. The specifications for many components continued to change after the primary support for ‘98 ended, and of course Microsoft has no interest in supporting a product when they can sell you a new one instead.