Some legacy software only works on Older versions of Windows. This is particularly true for various synthesizer-related editors and applications. Some of this software interfaces with external devices and may not work properly inside a virtual machine, so a Windows 98 install is often better with real hardware.
The Asus Eee PC 701 is a good candidate for a Windows 98 install. Many (but not all) things work and the install is mostly painless. I use it to run Yamedit for my TX81Z, the SoundDiver software bundled with the FS1r, and have used it to update the OS on some e-Mu rack modules.
The one thing that makes the install much easier is the Eee PC's great BIOS support for booting from USB.
A rough outline of the process is as follows:
The reason this process is fairly complicated is because Windows 98 doesn't properly support external USB CD-ROM drives.
Since the Eee PCs are fairly similar, this may work on other versions. The PC 701 is the only one I've tried this on.
I have not yet gotten network drivers to work, whether it be the internal ethernet, or the wireless. This hasn't been a problem because I had an old SohoWare USB wired network adapter (NUB110) sitting in a drawer and it had a working Windows 98 driver. It may also be possible to get the internal ethernet to work, but there are a number of USB options that will work if you can't make that happen.