Yes it is possible to install linux distribution on Dell Dimension 4550 and if you have never installed linux before then you can go off with OpenSuse which will be good for your this machine. OpenSuse will be easy to install on it. It will be more easy to use partition magic to remove your windows partition and install OpenSuse.
And what is the hardware configuration of this machine?
does dell have some type of code embedded in the BIOS to where you can only install windows on it.
No there is no code embedded in BIOS.