Hoping someone can throw a suggestion as to how to stop a problem that's
just started happening with my iMac screen.

I have an iMac Special Edition (graphite) running MacOS 9.1.

I've started getting bright and dark horizontal bands of mostly purplish
light across my screen. All different heights. In some applications, one of
these bands of purple light, a couple of millimetres in height, will follow
my cursor up and down the screen, the band extending to the right of the
cursor only.

Also, I seem to have lost some screen space, in that I now have two black
vertical strips (about a centimetre in width) down the left and right edges
extremes my screen, with the window tabs I had set up along the bottom of
the screen sinking so that I can now see only the top edge of the tabs. I
can correct this (not the bands of light problem) by going to the Monitor
control panel and playing with Geometry settings, but if I revert to Factory
Settings, the problem comes back.

Anyone know what's going on? Has my iMac reached its expiry date? Is my hard
disk in danger of crashing?? :-(

Any tips welcome...TIA...Steven