Hi all...

I am wondering is it possible to install more than 4 Linux distributions with windowz in a single machine ?

I got this doubt since we can make only 4 primary partitions on any harddrive...

I'm not sure. I think you would be limited to 4 primary partitions.

The MBR model limits you to 4 primary partitions, one of which might be of the special type "extended", inside that you can create as many logical units are you want, limited only by your OS capabilities.

I have no idea of the current state of other OSes, but linux can be installed in any kind of drive, it doesn't need to be a primary partition (to tell the truth, it doesn't even need to be a partition, you could use a raw drive to install it, just format let's say hda instead of hda1).

In plain English, you can install as many linuxes as you want, as long as it's a partition number that linux can handle and your bootloader can see. You will have to attend to the limitations of other OSes though, if any.

How about logical partitions ?

As said, you can install linux in whatever type of partition. That includes raw (non-partitioned) drives, primary partitions, and logical drives/partitions, so don't worry about that. You can even put it file systems inside of a file, just like most live distros do nowadays with squashfs images.

Whatever you do it's wise to install Windows first of course.

What @i92guboj states is true in the strictest sense, however there are limitations imposed for the "normal" user.
It is not unknown for Linux distro installers (the software) to insist on a primary partition - inane but true. Anaconda was a prime example.
Then there is (or was) a SCSI limitation of 15 partitions that the adoption of libata exposed (E)IDE disks to.

Will only use a primary partition :
Windows, BSD's , Solaris.

Partition 1, 2, 3 : primary.
Partition 4 : extended.
.. Logicals ..
Partition 5 : swap.
Partition 6...15 : All for Linux's

.. The above is what I most often use.
And I have never seen a Linux not working on a logical.
Anaconda : I have at least 9 Fedora's, CentOS, Scientific
on logical's
.....

O it's possible and many more too. HERE

you can although it's probably best not to, why would you wish to run four seperate linux based systems on a single machine, I can understand running solaris, windows, bsd and linux to test which is the best however Linux itself is just a different set of packages with each release around a kernel with common design features It would be like having windows 98, ME, 2000, XP and vista installed on one PC.

Another (somewhat) limiting factor is which bootloader you will be using. Don't quote me on the number, but LILO will IIRC boot a max of something like 24 or 28 OS's, while for GRUB the limit (if there is one) is much higher. There are several other bootloaders (including loadlin and ntloader) but I'm not familiar with them enough to comment. Also, the newest LILO may have a higher limit too.
Either way, those mentioned will boot many more OS's than is practical for any normal machine/user, but *everything* has its limit somewhere.

Sasha

pmsl @ > 20 OS's, is this for someone with multiple personalities

Thanks for pointing that out. Being on the Gentoo universe one sometimes forget how silly these installation wizards can be. I guess that's true, however as you very well point out, it's stupidity on the installer side. All the linux distros can -technically speaking- be installed on logical drives without any problem. The only problem is that circumventing a stupid install wizard might not be that trivial to the average user though, or even the experimented one.

Yes, I was aware of that, though I don't know what the current situation is. I was thinking on this exactly when I said above that the only limit on the partitions you can use is imposed by your OS.

The MBR standard itself, doesn't impose any limit on the number of logical partitions you can create inside an extended one. The way it's implemented certainly doesn't impose any limit. Whoever is interested in the details can read on EBR's (extended boot records).

The latter can boot off a logical partition since that limitation was fixed in a recent OpenSolaris update. I never tried it yet though.

Interesting news @jlliagre - do you have a reference ?. Not before time IMHO.
What about (Linux) swap partitions ?.