what can i use and what cant i use ? cheers guys

Can you rephase your question? I don't understand what you mean.

Do you mean you want to run Windows .exe files on Linux? Or do you want to be able to share files across both Windows and Linux filesystems?

none of them sorry... i wan tto know what file formatts will run ona linux system and what file will not for example i know .exe does not..

with the right program ALL file formats will run .
you might want to read
LINUX:
" Rute User's Tutorial and Exposition "
http://rute.2038bug.com/rute.html.gz

and
http://www.tldp.org/
http://www.howtoforge.com/

There are different packaging systems for different distributions. Some of the major packaging systems are rpm, deb, tgz. Rpm based distros like RH, SuSe, Mandriva and clones use these types of files for package installation. Debian based distros such as Ubuntu, Mint including Debian will use these files. Slackware and clones will use tgz.
And if the package for your distribution is not available, you can install it from source. The source files are usually in .tar.gz or .tar.bzip2 kinds.

This is a very generic question. In linux you can produce .exe file via Mono. But in general the files are of two forms executable and non-executable. There is no some special extension to inform you about the ability of running a file in linux. If you give the command ls -l you will see an 'x' in executable files.

Now, if by your question you mean if the executables of Windows can on linux then the answer is no.

Other file formats like pdf,jpeg,mp3 and etc are not executable. They depend on an application to run. For example you can view pdf files in linux using kpdf,okular,ghostview adobe reader for linux etc. You can view video files via vlc ,kaffeine etc. Konqueror to view jpeg files and in general there are many linux-apps out there for almost any file. Now if the file is of proprietary format eg iTunes or wmv then you may not be able to play the file. But there are always new applications in linux so must make this discussion per filetype.

File extensions are really nothing to Linux.

Data files can be opened as long as there's a program that can understand the format. Since there are virtually millions of file formats out there, we would have to concentrate on a few of them, and see if there are visors/editors for those files. Most commons graphics and sound formats can be opened without problems. Some restricted formats might be problematic, like drm'ed media player files (I don't have any interest in using drm'ed media anyway).

Exe files are not data files. They are programs. And windows programs can't be run in linux natively because they are two different OSes from the root, they are plainly not compatible. Nonetheless, you can try to run *some* windows programs under wine, which is a reimplementation of the Windows API on top of linux and xlib. Whether a concrete program will work (or how if at all) depends entirely on the program itself. You can always check the wine database:

http://appdb.winehq.org/

This has nothing to do with the file extensions however. You could name a linux program "foo.exe", but the internal format of the file would continue to be this of an ELF executable for linux, and not a Windows exe file.