A friend asked me how to do it, and I can't say for shure. All I know is that it should be in /boot/grub/menu.lst, and that windows should be on (hd0,0).
But how do you specify which system gets booted by default, and how long it should wait?
Just to clarify, windows and debian are already installed... it should only boot windows first after a few seconds.

I read through a grub howto, but I don't get it, I'm sorry. It sounds like the japanese translation of something.
If anybody could point me to a humenly readable grub-howto, that would be fine too.

In the config file there is the "default" option, which defines it. Value zero means the same as "first entry in the list". So, either put your Windows entry on top of the list (a good idea, if you update Linux kernel automatically so the grub config is edited automatically - this way Windows is always the first) or alter the "default" value to point to the Windows entry (set it 3 if Windows is the fourth on the list etc.)

get the GRUB manual here:
http://www.gnu.org/software/grub/manual/

Quite well written, actually---but still not light reading....

thanks, that did it.