Windows 98? Wow, thats one old computer!
Try restarting your computer.
If that didn't work, try uninstalling and re-installing Graal V6? To uninstall, go into your windows search in start and search uninstall. Click uninstall a program. After, go to Graal, and hit uninstall
If uninstalling doesn't work, install an application called Revo Uninstaller and uninstall Graal using this program. What Revo Uninstaller does is it uninstalls the program completly, meaning there is no traces of an uninstalled program left on your computer. When you uninstall a program using Windows Uninstaller, often it doesnt delete the entire program. It usually leaves settings, cache files and backups on your hard drive. With Revo Uninstaller, it completly removes a program at its entirety.
If that doesn't help, it could be that your computer is too old.
Hope this helps