The size should be large enough to hold the guest operating system and all of the software that you intend to install in the virtual machine, with room for data and growth. There is no way to increase this number later, although you can install additional virtual disks if you run out of space on this one. You will typically need about 500MB of actual free space on the file system containing the virtual disk to install Windows 98 and popular applications such as Microsoft Office inside the virtual machine. Enable the CD-ROM drive. Select CD-ROM Enabled.
Most operating systems require the use of a CD-ROM for installation.
If you wish, you can disable access to the CD-ROM drive later using the Devices menu. Enable the floppy disk drive. Some operating systems may require the use of a floppy drive during installation. If you wish, you can disable access to the floppy disk drive later using the Devices menu. Configure the networking capabilities of the virtual machine.