Stuck in Limbo between OS builds

Cyrix 586 166mhz machine. The owner was running Win98 but wanted to change it to Solaris 8 for intel. Discovered that building to Solaris 8 was not possible on his platform and tried to go back to Win98.
The machine informs him that there is already an operating system on the target disk and then hangs instead of completing the Win98 install. User claims some urgency in regaining the Win98 build (tax info on disk).