How to modify the startup menu ?

Grub passwords - http://www.gnu.org/software/grub/manual/html_node/Security.html
Hide - don't know
Remove - edit /boot/grub/menu.lst and remove windows entry

Hide... Well. In grub at boot time you can manually type in boot parameters. So if you write on a paper the 5 rows you need to type in, then you can delete you windows entry in '/boot/grub/menu.lst' and then type it manually, if you want to use it. :)

Is it a laptop? Because neither windows, nor linux aren't encrypted - linux can be, but windows definitely not -, and so your data's are not protected at all. Anyone takes the winchester out, plug's into another computer, and reads everything without any effort.
If it's a computer in the college - well maybe. But if so important to have a windows perfectly hidden, I would suggest a Virtual Machine like VMWare, or qemu. With that solution you can have a 10 GB file in your linux filesystem, which works in the Virtual Machine as your windows partition. And perfectly unmanageable outside from your linux. Then if you encrypt your linux partition's with something on the fly - I know this can be done, but I haven't used anything like that yet -, then your system will be PERFECTLY secure. And you will not need any grub password either. :)

The VMWare Fusion gives you 3d acceleration - for gaming -, and a special new feature to pack your existing windows partition into a VM image file, which you can port to any system. Imagine, it's not an Audio CD but a OS DVD, and still 'playable' anywhere. Cool huh? Although Fusion isn't free :(.

Best regard, Gábor.

Hide... Well. In grub at boot time you can manually type in boot parameters. So if you write on a paper the 5 rows you need to type in, then you can delete you windows entry in '/boot/grub/menu.lst' and then type it manually, if you want to use it. :)

Is it a laptop? Because neither windows, nor linux aren't encrypted - linux can be, but windows definitely not -, and so your data's are not protected at all. Anyone takes the winchester out, plug's into another computer, and reads everything without any effort.
If it's a computer in the college - well maybe. But if so important to have a windows perfectly hidden, I would suggest a Virtual Machine like VMWare, or qemu. With that solution you can have a 10 GB file in your linux filesystem, which works in the Virtual Machine as your windows partition. And perfectly unmanageable outside from your linux. Then if you encrypt your linux partition's with something on the fly - I know this can be done, but I haven't used anything like that yet -, then your system will be PERFECTLY secure. And you will not need any grub password either. :)

The VMWare Fusion gives you 3d acceleration - for gaming -, and a special new feature to pack your existing windows partition into a VM image file, which you can port to any system. Imagine, it's not an Audio CD but a OS DVD, and still 'playable' anywhere. Cool huh? Although Fusion isn't free :(.

Best regard, Gábor.

Well I just looked after the first suggested link, and realized, that
this has already solved the problem - in a quite elegantly way.
So Pierre please change this question's status to solved.

Thanks, Gábor.
2008. 04. 21, hétfő keltezéssel 00.09-kor Jason Sandlin ezt írta:
> Question #30238 on Ubuntu changed:
> https://answers.launchpad.net/ubuntu/+question/30238
>
> Jason Sandlin proposed the following answer:
> Edit your menu.lst file. Found at /boot/grub/menu/lst. You will need to be root to do so so open a terminal window and type gksu /boot/grub/menu/lst,
> Once it opens you should see somewhere in the file something like the following:
>
> ## hiddenmenu
> # Hides the menu by default (press ESC to see the menu)
> #hiddenmenu
>
> Just remover the hash in front of hiddenmenu
>
> ## hiddenmenu
> # Hides the menu by default (press ESC to see the menu)
> hiddenmenu
>
> Now when you boot you will not see the menu and your default OS will boot. You will see a something that say push ESC to enter boot menu and a timer counting from 10.
> To edit the amount of time it waits just change it to what you want. in the same file in this section:
>
> ## timeout sec
> # Set a timeout, in SEC seconds, before automatically booting the default entry
> # (normally the first entry defined).
> timeout 10
>
> Setting it to about 3 or 4 seconds will limit the time they have to
> respond but give you just enough time to hit is if you need to.
>
> You may also want to edit your fstab so the windows partition in not
> accessible from the linux OS.
>
> Hope this helps
>

Thanks Jason Sandlin, that solved my question.