Windows 98 has the drivers for the HP 540 Deskjet printer built in so you really don't require any other driver.
The driver attached is the only driver available at this time from HP. It should work with Windows 98. However, keep in mind that it is classed under Windows 95. If it doesn't work under 98, try the inbuilt drivers in Windows 98 by installing them from the printers section. Hope this helps.