I'm having some problems with line 6 (/dev/sda2 / ext3 defaults,errors=remount-ro 0 1). How is it with the spaces in it please? (which ones are tabs, which are regular spaces, and is it always just one space ore more?)

Consider all spaces as tabs, type /dev/sda2 then a tab, then '/' and a tab, 'ext3' and a tab, 'defaults,error=remount-ro' and a tab,'0' and a tab and finally '1'.

I did that, but I still get this at the startup screen in the recovery mode:

* Checking file systems...
fsck 1.39 (29-May-2006)
WARNING: bad format on line 6 of /etc/fstab

* Mounting local filesystems...
[17179585.100000] FAT: bogus number of reserved sectors
[17179585.160000] FAT: bogus logical sector size 65535
* Configuring network interfaces...
* Setting up console font and keymap...
root@jan-laptop:?#

When I then put in "init 3", gdm starts up. After mounting sda1 in /media/windows, I still can't access it...

Are the Windows partitions ntfs? Change line 6 so it reads
==> /dev/sda2 / ext3 defaults 0 0

Yes, the windows partition is ntfs.
I changed line 6 again, and the same thing came up on the startup screen, except that now the FAT numbers are [17179595.524000] and [17179595.520000]

Ok for the time being comment out line 6, by adding a '#' at the start of the line.

For the ntfs support, you need to install a package called ntfs-3g.
Method:
1) sudo apt-get install ntfs-3g
2) password: <-- enter your user password
3) reboot.

Oh and i forgot, replace 'vfat' in fstab with 'ntfs'.

I replaced vfat with ntfs in the case of sda1 (windows) and with ext3 in the case of sda4 (documents) because the partitiner frpm the Ubuntu instalation CD indentified it as such (hope that it's supposed to be like that).

trying to install the ntfs-3g package, I got this:

Reading package lists... Done
Reading state information... Done
E: Couldn't find packag ntfs-3g

What should I do, please?

Ahem., you know its actually kinda late here 2:30am, i have to sleep *yawn*, so hopefully someone else will help you.

But i give you this link, enjoy
Howto: Ntfs on Ubuntu

Alright, have a good night and thanx a lot once more...

Ok If you Want to use UUIDs and it is having issues with UUIDs then you can generate new UUIDs

This Is An Example The Same Values Will not Work for you:

Ok So Issue the Command uuidgen /dev/? ("?" Being The Partiton With the uuid in question)

root@bluecart-18:~# uuidgen /dev/sda1
74fb76f0-b29d-4051-80ce-c2a224b87240

So Basically on Ubuntu Edgy do a "nano /etc/fstab"

You Have Two Options You can remove all the uuids from the file.

Or Replace the uuids with new ones

Before:
UUID=860c61aa-356a-4ec1-bea3-d3fd88812922 / ext3 defaults,errors=remount-ro 0 1


Do this: uuidgen /dev/sda1
Copy The output and Replace the uuid for the partition you are using as "/" In /etc/fstab.

After:

UUID=efbd7aaf-98b6-4847-9bac-8d6f62e74858 / ext3 defaults,errors=remount-ro 0 1


Thats it.