Oks...
qfg1vga should work fine through windows 98 - it was released around that era of windows OS.
You mentioned that the game suddenly stopped working for you - I take that to mean at one point it was working fine... Am also going to assume you have an up to date virus scanner running on your system - if not get one quick
Some things to try:
Reinstall the game over your existing installation - this will rule out any file corruption.
If that doesn't cure it, then try uninstalling anything that has added new TSR's to your windows installation - i.e. anything you've installed that has added an icon to your systray, anything that has added to your autoexec.bat and config.sys files, anything that has added something to your "startup" folder.