On this forum we usually recommend
AVG for people looking for free anti-virus. And according to the product page it supports win 98. (I don't have a win 98 machine so I'll have to take their word for it.)
When it comes to anti-spyware you should have a look at
SUPERAntiSpyware, it also claims to support win 98. The only major downside to the free version is the lack of real time protection, you can only do manual scans. For me it doesn't really matter though. I practice safe surfing and only use superantispyware to do an occasional check up or to scan a suspicious file.