If a Windows 98 VM is configured to use the emulated USB tablet (absolute pointing device), the coordinate translation may be incorrect and the pointer is restricted to the upper left quarter of the guest's screen.

The USB HID (Human Interface Device) drivers in Windows 98 are very old and do not handle tablets in the same way as modern operating systems do. To work around the problem, use the following command:

$ VBoxManage setextradata VM-name "VBoxInternal/USB/HidMouse/0/Config/CoordShift" 0

To restore the default behavior, remove the key or set its value to 1.