Installing Programs?

your question isn't clear. what do you mean by "i want to download a program which the download options stands between Mac osx and Windows"?

for example itunes or something, when i will download that it says i need to choose operating system, and i can only choose between the apple operating system and windows, there's no ubuntu option? what do i do to get the program :-)?

Itunes is an unfortunate example -- it does not run on linux, as apple do not provide such a version. However, you can still often connect to your apple devices (these run a proprietary undocumented protocol from apple, rather than the standard mass storage protocols) using software provided with ubuntu, such as rhythmbox and amarok.

http://www.psychocats.net/ubuntu/itunes

It is usually best to select from software shipped with ubuntu, or otherwise designed for your platform. Otherwise, you can sometimes use "wine" (windows emulator) to run windows programs -- however this is a "best effort" system, and cannot be guaranteed to work with any specific program. A database of common programs, and how well the function with wine is maintained here:

 http://appdb.winehq.org/

So i can only use programs with ubuntu, that is also made for ubuntu ? Because i use many programs now wich i cant download as an ubuntu version :-/

>So i can only use programs with ubuntu, that is also made for ubuntu ?
No, you can still use some non ubuntu (or rather, windows) programs through wine -- many programs *will* work, but not all. You need to consult the appdb database link.

 http://appdb.winehq.org/

If you use PlayOnLinux (a front end for Wine) it claims to load iTunes 7 and/or iTunes 10.