After 5 years of service my Sager 8890 is starting to have Video issues.

My diagnosis so far:

• my display shows "artifacts", mostly around the mouse pointer and window borders
• the problem doesn't seem to be in my display because it occurs on the external monitor as well
• the problem doesn't seem driver or OS related because it already occurs during boot and affects both XP and Vista systems

I hope repair is possible. I may need a new or refurbished Motherboard.

Any clues?

Your graphics card is failing.

At least this seems the obvious answer. It's repairable but maybe not worth it. You may be able to find a replacement on eBay if you feel comfortable with a screwdriver and some thermal paste it should be something you can do yourself.