Me too, guess it's a Win2k or later file. The last version that does work (for me) for W98 is 5.0 :WG511T Software Version 5.0
You get an odd message (like 5.2) when installing that says you must be admin, but just say OK, it doesn't stop anything.
I'm using a dual boot W98/W2K Vaio (old) laptop and I was getting better throughput in 2000 with V5.2. Also the country setting wasn't being remembered in v5.0, so I thought I give the latest version a try. Didn't work...
Got the missing 'asupplicant.dll', which brought me to this forum. I too used to use v4.4 (and previously whatever was in the box) but 5.0 has been working for me since August 2007, so I'm thankful it's stable.
As an aside, when I went to the Netgear support site to check system requirements today, I left them an "unhelpful" comment that, they should say what works with W98.
Hope 5.0 works for you.
PS. Here's the About Box (not shown on support page and versions don't seem to tally with what they say either)