Tested with Bochs 2.6.6 on Windows Vista SP2.
Copy the sample config to a production config:
COPY bochsrc-sample.txt bochsrc.txt
Create an 8 GB image file:
bximage -mode=create -hd=8G "D:\QEMU VMs\Windows 98 SE NL\Win98SENL.img" -q
Add to bochsrc.txt:
ata0-master: type=disk, path="D:\QEMU VMs\Windows 98 SE NL\Win98SENL.img", mode=flat ata0-slave: type=cdrom, path="D:\ISO\Win98\WINDOWS 98.ISO", status=inserted
Set the BXSHARE variable to the Bochs install directory and start bochs:
SET BXSHARE=D:\Apps\Bochs-2.6.6 bochs