[harry2sally]

I have switched off my iMac by selecting shut-down in WinVista. This morning I wanted to use Vista again, but when I started my iMac it showed the little green moving bar, a flicker of a blue screen and then rebooted. Then I selected the safe-mode boot (and some of the others), but blue-screen flicker and reboot again. When I used the Vista CD, the tool did not show me the Vista partition. However, when I go into MacOS, I can see and access the partition with all the files on it.
This is now the second this happened and the first time I reinstalled everything.
Rather than re-installing, I really would like to know whether there is a better (and shorter) way to repair whatever setting has gone wrong. Thanks for your help.

[seanc]

Boot the iMac and choose to boot the Vista partition, as soon as it changes to a black screen, start repeatedly pressing F8 - this should bring up a menu. One of the options should be to disable automatic restart. Select this, press enter and wait for it to try and boot. It should now stay on the blue screen rather than restarting.

What does the blue screen say? Can you take a clear photo and post it here?