Graphics Artifacts (kinda) different in Ubuntu than in Windows

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http://ubuntuforums.org – Apologies for the wacky title, it was the most concise that I could come up with... :) I've inherited some old but decent hardware and have installed Ubuntu happily alongside Windows. Everything's fine except graphics - there's some weird stuff going on that I have a feeling just means "busted graphics card". I've attached some pics. The boot screen is rather weird, it varies from boot-to-boot, today's one is rather good comparatively... CAM00133.jpg The black/white dotty screen capture is actually from OpenTTD running full screen on Windows - for some reason the game didn't appe (Hardware)