Question : Convert Old computer to a server running 2003 or 2008 Windows server

I would like to take an old computer great running condition
wipe drive and only run windows server 2003 or 2008 and a medical billing program

Will it be fast enough and hearty enough to do this . 5 computers would be accessing its data for medical billing program

The computer chip  is a 3.33 gigahertz intel Celeron D
16 kilobyte cache
512 secondary cache  
Bus clock 133 megahertz
Bios American Trends Inc. 5.04 from 11/30/2006
memory 1408 ram

Answer : Convert Old computer to a server running 2003 or 2008 Windows server

Well, I would not go with 2008 given the specs you listed.  2003 would be better suited for this; though I would try to double the amount of memory installed.  the system will work, but it all depends on the software you have installed that users will access.  If it is a sql setup, then your system will run very slow, almost to the point of not being worth it.

My recommendation is to forget this system and find another that is more powerful.  You will thank yourself later for it.