I'm not sure how Vista works in dual boot but if it's anything like XP you will need a partition for Vista and a partition for 98. I'm not sure if you can use a "recovery partition" for one of them.

I have been most successful installing Windows 98 FIRST on the primary partition and then installing XP on the secondary partition. XP will recognize the 98 partition and build the boot environment to include both partitions.

There are a number of articles over at microsoft.com on the subject of dual boot. I would do a search over there to get more information. They will probably have more specifics on Vista/98 dual boot than I can provide.