exchange 2003

all you have to do is look at the system requirments.  it has to be installed on a 2003 domain, but the box can be a 2000 server.  IE the server you install exchange 2003 on can be a windows 2000 or 2003 box, but that box must be a member of a 2003 domain. See below:

http://www.microsoft.com/uk/windowsserversystem/exchange/product-information/system-requirements.mspx

i only have one box and it is 2000 server so obviusly my domain is in 2000

The article Mikeleebrala points to is correct:  you can run E2K on in a Win2K3 domain (as he has done), but you *cannot* run it on a Win2K3 server (only on a Win2K server in a Win2K3 domain.).  

So the answer to Gianitoo's original question is "yes."

carlo... he is trying to install exchange 2003 in a windows 2000 domain, not e2k in a w2k3 domain like you mentioned.

Yes, I understand that.  The answer is "yes", he can run E2K3 on a Win2K server using a Win2K domain.  This is clear in the link you provided, and in the original  Microsoft document, which here:
http://www.microsoft.com/exchange/evaluation/tiwinnet.mspx

I beg to differ..

I have a Windows Server 2003 running in a Windows 2000 domain, using a clustered Microsoft Exchange 2003 Server as our mail server, which was upgraded some 6 months ago, from Exchange 2000, and had no problems (touch wood) as of yet.

If you differ, please explain why.  The documentation seems clear to me.  

SeanUK777   i agree with carlo,,,, all you are doing is agreeing with him. The document that carlo posted clearly said that you can run exchange 2003 in either a windows 2000 or windows 2003 domain, on either a 2000 or 2003 box,  which is the same thing you just said.  

oops, i was reading a cached copy, didn't see the other comments..
So, I am agreeing then..